Zimmun (1)

  • Deracheha Staff; Laurie Novick, Director
By Laurie Novick, with research by Rivka Mandelbaum;
Rav Ezra Bick, Ilana Elzufon, and Shayna Goldberg, eds.
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What is the mitzva of zimmun? Who is obligated? Under what circumstances do women recite it?
The Nature of Zimmun
Under certain circumstances when eating with others, the obligation to recite birkat ha-mazon includes zimmun (lit., convocation). What is zimmun? A multifaceted beracha, with two primary functions:
First, it invites a group of people to unite in recitation of birkat ha-mazon. Kolbo elaborates on the opportunity that zimmun provides to invite and prepare individuals to praise God as a group:
Sefer Kolbo 25
The matter of the zimmun is the increase of praise and greatness to God, that they invite and alert each other and join together to thank Him and praise Him for the bounty of His goodness, as it is written (Tehillim 34:4) “Let us exalt His name together.”
Second, zimmun transforms birkat ha-mazon into a communal ritual. Rashi makes this point in a comment noting that there is a distinction between reciting birkat ha-mazon following zimmun and merely discharging another's obligation in birkat ha-mazon:
Rashi Berachot 45b s.v. Ve-amar Rabbi Zeira
…Since [when only two people eat together] one person discharges his obligation through his fellow’s recitation of birkat ha-mazon, we learn that there is no zimmun [with only two people]. For if there were a zimmun, the beracha would be of both together, for [one] says “Let us bless” and [the other] answers “Blessed be He.”
When one person discharges another's obligation, they each fulfill an individual obligation at the same time. Zimmun, however, means that the beracha is theirs together.[1]
Presumably based on this communal understanding of zimmun, Rambam writes that a mezammen (person leading zimmun) should recite all of birkat ha-mazon aloud for all participants.
Rambam, Laws of Berachot 5:2-3
What is the beracha of zimmun? … One of them blesses and says “Let us bless from Whom we have eaten,” and all answer “Blessed is He from Whom we have eaten and through Whose goodness we live.” Afterwards, he says “Blessed are You, Lord our God, King of the world, who sustains the entire world with His goodness…” until he finishes the four berachot [of birkat ha-mazon], and they answer “Amen” after each beracha.
Rambam's suggestion is unfortunately difficult to put into practice because it requires great concentration on the part of the participants. Some do take care, though, to have the mezammen recite all of birkat ha-mazon aloud, while others pause to hear the mezammen recite the ending formula of at least the first beracha.[2]
The Talmud seems to present two other possibilities as the minimum for discharging the obligation of zimmun: joining only for the zimmun formula, or joining through the end of birkat ha-zan.[3] 
In practice, Shulchan Aruch rules that the minimum is to hear the zimmun formula itself, emphasizing its role as invitation and introduction, while Rema rules that one should be sure to participate, or at least answer amen, through the end of birkat ha-zan.[4] We will see that the idea that the mezammen should, at least in theory, be able to discharge the obligation of birkat ha-mazon for all zimmun participants has halachic implications.
Before turning to those implications, we need to look more closely at the mitzva of zimmun, its source and meaning.
In many cases, we are obligated in the communal endeavor of reciting birkat ha-zimmun. The Talmud records a debate as to whether we derive this obligation alongside the obligation to recite birkat ha-mazon itself.
Berachot 48a
Our rabbis taught [in a baraita]: Whence do we know that birkat ha-mazon is from the Torah? For it is said… “[bless] the Lord your God” (Devarim 8:10) this is birkat ha-zimmun… Rabbi [Yehuda Ha-nassi] says: This is unnecessary. …birkat ha-zimmun derives from “Gadelu la-Shem iti [u-neromema Shemo yachdav]” “Give greatness to God with me [and let us exalt His name together]” (Tehillim 34:4).
According to the first view, zimmun may be obligatory on a Torah level; the verse suggests that it helps welcome God's presence to our recitation of birkat ha-mazon. According to the second view, ascribed to Rabbi Yehuda Ha-nassi, the obligation in zimmun is derived from a verse in Tehillim, and urges us to praise God together.
Some early authorities, including Ra’avad, do conclude that zimmun is obligatory on a Torah level,[5] while others, including Ra'ah, maintain that it is rabbinic.[6] A third position, proposed by Mabit, suggests that zimmun is obligatory on a Torah level specifically when recited by at least ten men.[7] (We'll come back to the question of gender for this type of zimmun in the second part of this series.)
Another Talmudic passage offers two possible Biblical derivations for the obligation in zimmun to apply when at least three people have eaten together. One of the verses is the same one cited by Rabbi Yehuda Ha-nassi above. In both verses, the speaker— one person— uses plural language to invite at least two others to praise God. One speaker plus two (or more) leads us to three (or more).
Berachot 45a
Mishna: Three who ate as one are obligated to recite zimmun. … Gemara: From where do we derive these things? Rav Asi said: As the verse says “Give greatness to God with me and let us exalt His name together” (Tehillim 34:4). Rabbi Abahu says from here: "Ki shem Hashem ekra, havu godel l-Elokeinu" “For I will call upon the Lord’s name; give greatness to our God” (Devarim 32:3).
Both verses align with the structure of zimmun, in which a single mezammen leads, while others participate in praising God. A closer look reveals that each verse highlights one of the primary functions of zimmun: "For I will call upon the Lord’s name" focuses on the role of the speaker in inviting others to prepare themselves and join in the praise. As above, "Give greatness to God with me" emphasizes reciting praise of God together in a communal ritual. Rav Soloveitchik elaborates on what this means:
R. Joseph B. Soloveitchik, “An Exalted Evening: The Seder Night,” in Festival of Freedom, ed. Joel B. Wolowelsky and Reuven Ziegler (Ktav: 2006), p. 21.
The idea which this halakhah tries to translate into a ceremonial is that of a community formed by the act of eating. The se’udah is designed not only to satisfy man’s physical needs, but also to take him out of his sheltered seclusion and loneliness and let him join the thou. Eating becomes a cohesive force bringing together people who were shut up in their own small worlds and coalescing them into a community. The Halakhah is aware of the fact that a meal partaken together unites people, fosters friendship, and fashions a company of eaters that may, in the long run, become a community of God-seekers and the God-committed.
Zimmun forges, elevates, and even celebrates community in blessing God.
Blessing Together
What exactly is the nature of a communal beracha, and how do we define a community of eaters who can make one?
Let’s start by looking at the berachot we recite over a physical benefit (birchot ha-nehenin). Generally speaking, a person cannot recite such a beracha for another unless personally experiencing the same benefit.[8] This works well enough for a completely shared experience, such as smelling the same incense together.
When the benefit in question is eating, though, the shared experience only goes so far, because the act of eating is essentially individual, and thus each person receives benefit from the food in a distinct way. The Talmud Yerushalmi points out that this complicates the halachot of reciting a beracha before eating or drinking.
Talmud Yerushalmi Berachot 6:6
What is the difference between incense and wine? Incense, everyone smells. Wine, [each] one tastes.
Therefore, the mishna teaches that one person only recites a beracha on behalf of others before eating if they have reclined together (in Mishnaic times, the common mode of eating a formal meal). The Talmud makes clear that a shared experience of eating communally, eating as a chavura, is at issue here. A chavura is typically defined as constituting three or more members.[9]
Berachot 42a-b
Mishna: If they were sitting, each one recites a beracha on his own. If they reclined, one recites a beracha for all of them. Gemara: ….If they reclined, yes; if they did not recline, no. They raised an objection: Ten who were walking on the road, even though all of them were eating from one loaf, each one recites a beracha for himself; if they sat down to eat, even though each one of them eats from his own loaf, one person recites a beracha for all of them. It is taught “they sat” even though they did not recline! Rav Nachman bar Yitzchak said: In a case when they said: Let’s go and eat in such-and-such a place.
Even if they don't recline, a group's verbal agreement to eat together in a specific place can define them as a chavura. Rashi explains that this verbal agreement is a sort of hazmana, designation, which lends the communal eating fully established status, kevi'ut.
Rashi Berachot 42b s.v. Be-duch pelan
In such-and-such a place, for they established a place for themselves in advance with speech, counsel, and designation [hazmana]– this is kevi’ut. But if they sat down on their own in one place together – it is not kevi’ut.
Tosafot add that once reclining is no longer the norm, sitting around a single table to eat bread can suffice to allow for a single, communal recitation of ha-motzi.
Tosafot Berachot 42a s.v. hesevu echad mevarech le-chulan
If they reclined, one recites a beracha for all of them. – We do not have reclining except with bread alone, and bread is effective even without reclining. For specifically for them, because they ate reclining, they required reclining. But our sitting is kevi’ut for us as reclining was for them, for they were accustomed for each one to recline on his couch at his table, but now all of us eat at one table and when we eat together, that is our kevi’ut.
Additionally, within a person's home, all household members who eat in the same general space are automatically considered a chavura.[10] Shulchan Aruch summarizes these halachot, narrowing the application to birkat ha-motzi recited over bread, since eating bread is itself a sign of eating with kevi'ut:
Shulchan Aruch OC 167:11
If they were two or many, one recites the beracha for all of them, and specifically if they reclined, which is the manner of keva (Rema – or a householder with members of his household, which is as if they reclined-Tur). But if they were sitting without reclining, since they are not established [nikba’im] together, each one recites a beracha for himself. If they said, “let’s eat here, or in such-and-such a place,” since they prepared a place to eat, this constitutes keva even without reclining. Nowadays, when we are not accustomed to recline, our sitting at one table, or without a table with one (table)cloth is kevi’ut, and even for members of a chavura it is like their reclining. For us, even if they established a place for their eating, or a householder with the members of his household, it is not effective unless they sat at one table or one (table)cloth.
In practice, when a group of people sit down together to eat bread they are considered a chavura as long as they are not scattered.[11] The halacha is even more flexible regarding household members eating together, since they all, in a sense, eat at the same table even when not literally doing so.
When a chavura discharges its obligation in birkat ha-motzi through one person's recitation and others responding amen, the beracha itself is communal, representing each member of the community who have come together as a single halachic body.
Ra’ah Berachot 42b
Know a general principle regarding birchot ha-nehenin…one [person] does not discharge [others’ obligations] except when they are in a manner of kevi’ut and chavura, because they are like a single body, and it is considered as if each one of them recites the beracha
This recitation of ha-motzi on behalf of the community is akin to the communal form of birkat ha-mazon created through zimmun.
After the meal
The definitions of chavura for reciting a single birkat ha-motzi largely apply to reciting zimmun after the meal as well. Though his view is rejected in practice, Rashi even suggests that two people are not enough to combine for one beracha of ha-motzi, just as two do not generally suffice for a zimmun:
Rashi Berachot 45b s.v. mitzva leichalek
[Two who ate as one] it is a mitzva to separate – and for each one to bless separately, both for birkat ha-motzi and for birkat ha-mazon.
In the continuation of the passage we saw above, Tosafot teach that reclining establishes a group as a chavura, whether for birkat ha-motzi or birkat ha-mazon:
Tosafot Berachot 42a s.v. hesevu
If they reclined, one recites a beracha for all of them…. In the gemara, this is understood to apply both to birkat ha-motzi and to birkat ha-mazon
One unique feature of zimmun is that, once the obligation exists, it cannot be broken in such a way that all or any of those obligated will be unable to participate in a zimmun. So, for example, the mishna teaches that a group of three, four, or five who ate together may not separate, though group of six may separate into two groups of three.
Mishna Berachot 7:4
Three who ate as one are not permitted to separate, and similarly four, and similarly five. Six [may] separate…
Shulchan Aruch applies this halacha once the group has had a communal birkat ha-motzi, even before they have eaten together.
Shulchan Aruch OC 193:4
Three who sat down to eat and recited birkat ha-motzi…even if they have not yet eaten a ke-zayit of bread, they are not permitted to separate.
According to some opinions, the obligation in zimmun takes effect even if they have simply agreed to eat together as a chavura.[12] In some cases, our sages were stringent to obligate groups in reciting zimmun, making the criteria for considering a group a chavura more flexible than for a communal ha-motzi.[13]
Ramban goes so far as to suggest that a group can be considered a chavura for zimmun even without any formal kevi’ut.
Chiddushei Ha-Ramban Berachot 50a
We have further explained above (45a) that there is no requirement for three who ate as one for reclining or for kevi’ut of a place, but all those who ate as one recite zimmun.
In practice, people who began eating separately, and joined together only after initial berachot were recited, are also considered a chavura with respect to zimmun, as long as they finish eating together.[14]
Shulchan Aruch OC 193:2
Even if they were not all established from the beginning to eat together … they are not permitted to separate, since they become established together at the end of the eating…
It's even enough for two to finish eating to require the third member of the chavura to pause his eating and join the zimmun.[15] A final case in which a group can make zimmun is when each member became obligated to make zimmun with other groups and didn't yet recite it before coming together.[16]This last case is striking because the chavura in question never ate together at all!
Why should the definition of chavura for zimmun be more flexible in some cases than for reciting a communal ha-motzi?
The built-in call and response invitation aspect of zimmun itself establishes a distinct kevi’ut for members, analogous but not identical to the verbal declaration of intent to eat together. The halachic ideal may be to begin and eat a meal with the same chavura, but birkat ha-zimmun has communal elements that birkat ha-motzi does not. Any recitation of zimmun both depends on the presence of community and formalizes it, and the language of zimmun directly refers to that community by saying "nevarech," "let's bless."
Who is obligated to form a chavura for zimmun? One baraita teaches that "all" are, while another relates that a group of women recite their own zimmun. The Talmud in Arachin links the two baraitot together:
Arachin 3a
All are obligated in zimmun” – to include what? [What additional class of people is included in the obligation of zimmun by virtue of the word “all”?] To include women and bondsmen, as it is taught [in a baraita]: “Women recite a zimmun for themselves, and bondsmen recite a zimmun for themselves.”
A simple reading of the linking of the baraitot in this passage indicates that a chavura of women are obligated to make zimmun for themselves. Rabbeinu Asher rules this way, since he sees no reason why women should be exempt from the obligation of zimmun:[17]
Rosh Berachot 7:4
It seems to me that the passage in Arachin must be read as obligating, for it includes them [women in obligation], as it is taught “all are obligated”…Furthermore, since women are obligated in birkat ha-mazon, either on a Torah level or rabbinically, why shouldn’t they be obligated in zimmun like men?
This assertion is complicated for Tosafot, however, by the fact that it was rare for women of their time to recite zimmun. For this reason, they revisit the texts and come to the conclusion that the baraita means that women may opt to fulfill the mitzva of zimmun, but are not obligated to do so. They further support their reading by quoting the continuation of the baraita as it appears in Berachot:
Berachot 45b
Women recite a zimmun for themselves, and bondsmen recite a zimmun for themselves. Women, bondsmen, and minors, if they wish to recite a zimmun [together]– they do not recite a zimmun.
The simple meaning of this baraita is that three women or three bondsmen may form a zimmun, but a combination of women, bondsmen, and minors may not, even if they wish. Tosafot cite the phrase “if they wish” to suggest that the all-women's zimmun at the beginning of the baraita is also optional.
Tosafot 45b s.v. Shani
It is difficult, why are they [women] not accustomed [to recite zimmun]? From what is taught “they recite zimmun” it sounds as though “they are obligated to recite zimmun.” One can answer that “women recite zimmun for themselves” – is if they wish to recite zimmun, they recite zimmun. And this is slightly the meaning of the language is taught afterwards, “women, bondsmen, and minors, if they wish to recite a zimmun – they do not recite a zimmun” … And what is said at the beginning of Arachin (3a), “All are obligated in zimmun” to include women” is said as a voluntary matter and not as an obligatory matter.
Though Tosafot seem confident that their reading is consistent with the passage in Arachin, they don't fully explain how. What does a group of women's option to recite zimmun have to do with "all" being obligated in it? Semag fills this gap by quoting Ri, a major Tosafist:
Sefer Mitzvot Gadol, Positive Mitzvot, Siman 27
…Women recite zimmun for themselves as we learn in the first chapter of Arachin (3a, see Tosafot there), "all are obligated in zimmun to include women and bondsmen, as it is taught, women recite zimmun for themselves and bondsmen for themselves." And it is a question for in the beginning of “Three who ate” [Berachot chapter 7], he concludes that women reciting zimmun for themselves is voluntary. And Ri says that specifically for themselves it is voluntary, but when they eat with men they [women] are obligated and discharge their obligation with our [men’s] zimmun, and do not bless [birkat ha-mazon] for themselves. And sometimes Ri would tell women not to bless [birkat ha-mazon on their own when eating with men], and they would discharge their obligation with the men’s zimmun.
According to this reading, the passage in Arachin teaches us that women are only obligated in zimmun when eating with three or more men. However, for a chavura consisting only of women, zimmun is optional.
Why should this be the case? Perhaps for the same reason that women did not commonly perform zimmun voluntarily:
Mishna Berura 199:16
One can say that the reason the sages did not wish to impose on them [women] the obligation of birkat ha-zimmun when they are on their own is because it is not so common for them to be proficient in birkat ha-zimmun.
Assuming that women's obligation in zimmun is rabbinic, our sages could choose to exempt women, who might lack familiarity with the language of zimmun. This lack would not be a bar to fulfilling the obligation in the presence of a zimmun of men.
In Practice
Shulchan Aruch follows Semag's approach, ruling that an all-women's zimmun is voluntary, but that a woman is obligated in zimmun in the presence of a men's zimmun.
Shulchan Aruch OC 199:7
Women recite zimmun for themselves, as a reshut [voluntary matter]. But when they eat with the men, they are obligated and discharge their obligation with our zimmun.
In this case, the woman discharges her obligation by joining the men's zimmun.
I. An All-Women's Zimmun The view that an all-women's zimmun is voluntary has been widely accepted. Gera, however, rules in accordance with the view that three of more women breaking bread together are obligated in zimmun:
Bei’ur Ha-Gera OC 199
… Rosh’s words are primary, and thus wrote Talmidei Rabbeinu Yona, see there.
In light of this view, Ben Ish Chai encourages women to recite zimmun when eating together, even though women's zimmun was not practiced in many communities:[18]
Ben Ish Chai Parshat Korach 13
It is fitting that every man should teach the women of his household that they should recite zimmun for themselves when they eat in [a group of] three.
There is some halachic discussion about whether three or more women should recite zimmun in the presence of one or two men. Rav Moshe Sternbuch discourages this practice. In his view, men and women don't combine to create a zimmun out of tzeniut concerns (a point we discuss in our next installment), and the three women would not remain obligated in zimmun at a table where the men are exempt. He adds that women should not opt to recite zimmun when not obligated because it might be considered haughtiness, deviation from communal custom, or even a beracha le-vatala, blessing in vain.
Teshuvot Ve-hanhagot 4:51
It seems in my humble opinion to be inclined to think that, despite the opinion of Gera that “women recite zimmun for themselves” is an obligation, that is when they are by “themselves,” meaning, there are no men with them, but when they are with men … the women are not obligated in zimmun. For the obligation of zimmun falls on all those who are eating as one unit, but when they are together with men, which requires modesty, since they are not considered as if all of them have eaten as one, they are no longer obligated in zimmun. And even where there are three women alone and no need to include the men [present], in any case the sages did not make a distinction that the women should be obligated and the men exempt…And I was asked, if they [women] want to be stringent and to recite zimmun in order to avoid any doubt, are they acting properly. In my humble opinion, there are several reasons to be concerned about this. One, lest there be in this a suspicion of yuhara [spiritual haughtiness], and furthermore that three are called many and if so perhaps this has an aspect of “lo titgodedu” [the prohibition of forming factions] when a few adopt a stringency against the custom of the city, and furthermore in my humble opinion one should be concerned here about the prohibition of beracha le’vatala
Rav Dovid Cohen rules that the men in theory could respond with the words traditionally recited by one who has not eaten at a meal: "baruch u-mvorach shemo tamid le-olam va-ed," but in practice they should not do so.[19]
In contrast, Rav Shlomo Zalman Auerbach maintains that a group of women may recite their own zimmun even when one or two men are present. In that case, he rules that a woman should lead the zimmun — and the men should answer her.
Rav David Auerbach, Halichot Beitah 12:7 and n. 14
Three women who ate together with one or two men, it is proper for one of them to recite birkat ha-zimmun and not the man, but certainly the man is permitted to respond after them…[n. 14] …From my uncle Rav Shlomo Zalman I heard that if the women are proficient in reciting zimmun for themselves, it is not proper le-chat’chila (ab initio) [for the man] to discharge the obligation of someone who is proficient in blessing for himself [the women]… but it seems simple that also for a man, even if he does not have an obligation of zimmun as above, in any case he can answer after them [the women]… and thus I heard from my uncle Rav Shlomo Zalman.
This was also Rav Aharon Lichtenstein's view.[20] In this case, though the men answer birkat ha-zimmun, they recite birkat ha-mazon to themselves, because a woman's obligation in birkat ha-mazon may be rabbinic, affecting her ability to discharge a man's obligation.
II. In Presence of Men's Zimmun  When women eat in the presence of three or more men, thus becoming obligated in zimmun, Kaf Ha-chayyim rules that one of the men should recite it. This is because zimmun entails being able to discharge the whole group's obligation in birkat ha-mazon, and women might only be obligated in birkat ha-mazon on a rabbinic level.[21]
Kaf Ha-chayyim OC 199:24
 “They discharge their obligation with our zimmun.” Meaning that specifically the men recite birkat ha-zimmun and the women discharge their obligation, but not the reverse, that the women recite birkat ha-zimmun and the men discharge their obligation. The reason seems to me because there is doubt whether the women are obligated on a Torah level.
We saw above that Ri would caution women not to recite birkat ha-mazon on her own in the presence of men's zimmun, but rather to answer to the zimmun and join the group for birkat ha-mazon. In practice many are lax on this point. Rav Moshe Feinstein wrote a responsum to be melamed zechut, to judge groups in which women do not join a men's zimmun favorably, since a woman may be preoccupied with laying out a meal or caring for children, which gets in the way of formal kevi'ut as a chavura.
Responsa Iggerot Moshe OC 5:9:10
If women who ate with three men are obligated to answer birkat ha-zimmun: In the matter of women who ate at the table with three men, they are obligated to answer birkat ha-zimmun, as is clear in SA 199:7. But on weekdays, when in most places there isn’t an established meal where everyone eats together, and she is busy with preparing food and bringing it to the table for everyone, she does not intend to sit and eat together [with them]. All the more so when there are little children keeping her busy, and she does not have time for a fixed meal even on her own— and all the more so with others— on weekdays when everyone is rushing to eat. For if so, she has no connection at all to their eating. From this we can infer that even if it happens sometimes that also the woman had time to eat with kevi’ut, women did not become habituated to answer zimmun.
Rav Moshe only applies this justification on weekdays, when meals tend to be less formal.[22] In general, women should make every effort to participate in zimmun and men should take care to include women who have eaten with them in the zimmun, even if it means waiting for the women to return to the table.
An exception is when three or more women eat with between three and nine men. In that case, the women are permitted to break off and form a separate zimmun, just as a group of three men may form their own zimmun when there are another three to six men present.
Shulchan Aruch Ha-rav OC 199:6
Women who eat with three men who are obligated to recite zimmun, are also obligated to recite zimmun with them. And if they are three [women] and want to separate to recite zimmun for themselves, they are permitted to (if the men are fewer than ten and are not reciting zimmun with God’s name…).
Since women eating in the presence of a group of men are obligated in zimmun, an all-women's break-off zimmun is considered fulfillment of the obligation for those women.[23]
Why isn't women's zimmun more commonplace?
Even if we do not follow the opinion that women's zimmun is obligatory, it remains a halachic option, and we embrace women' voluntary observances in many realms. However, from Tosafot to Aruch Ha-shulchan, it is clear that it was uncommon for many women of past generations to recite zimmun.
This likely had something to do with lack of education. In our time, women are blessed with much more widespread opportunities to receive a Jewish education. Why, then, haven't more women practiced zimmun?
Perhaps because women don't know that it is a valid halachic possibility and are concerned that it may have controversial overtones. Or perhaps because leading a ritual is considered to rest firmly in the province of males. Or maybe simply because the text printed in benchers usually uses exclusively male language.
Whatever the reason, the message gets across that zimmun is not for women. As a corrollary, as Dr. Meirav Tubul Cahana points out, women may be reluctant to recite zimmun for fear of being labeled as feminists:
Meirav Tubul Cahana, “Women in Birkat Ha-Mazon,” Talelei Orot 15, 5769.
In recent years, we've born witness to a growing phenomenon of women who have eaten together and become obligated in birkat ha-mazon reciting [an all-women's] zimmun before the beracha. At the same time, I occasionally hear from my students that they are not accustomed to doing this, based on the rationale that “we're not feminist.” [The opportunity] to clarify the halacha of the relevance of birkat ha-zimmun to women gets missed…
Honoring customs and respecting people's comfort is very important. These are good reasons not to compel women to recite zimmun. Not teaching or encouraging women to recite zimmun, however, at least when eating only among women, is more difficult to comprehend, especially since there may be an obligation.
As Dr. Tubul Cahana notes, zimmun has become more mainstream and even routine in an increasing number of settings, a trend bound to increase as more men and women learn more about it.
Further Reading
Meirav Tubul Cahana, “Women in Birkat Ha-Mazon,” Talelei Orot 15, 5769.
Wolowelsky, Joel B., "The Eating Fellowship: An Exploration" Tradition 16:3 (Spring, 1977), pp. 75-82. Available here: https://traditiononline.org/the-eating-fellowship-an-exploration/
Zivotofsky, Ari Z. and Naomi, "What's Right with Women and Zimmun" Judaism, Sept. 22, 1993. Available here: https://www.thefreelibrary.com/What%27s+right+with+women+and+zimmun-a014873623

[1] Rav Yosef Dov Soloveitchick, "In the Matter of One Recites Birkat Ha-mazon for All" Shiurim in Memory of my Father and Teacher II
…Within birkat ha-mazon itself, two chaluyot [instantiations] of beracha are mentioned: (a) the entity of birkat ha-mazon of individuals, according to the directive of the verse “and you shall eat and be satisfied and bless” (in the singular); (b) the entity of birkat ha-mazon in a chavura [group] through zimmun, according to the directive of the verse “give greatness to God with me and let us exalt His name together” (Tehillim 34:4) regarding which the instantiation of the fulfilment of “together” is the ultimate foundation. The instantiation of zimmun is fixed in the essence of birkat ha-mazon, which constitutes a unique entity of birkat ha-mazon be-zimmun, instantiating “together.”
[2] Mishna Berura 183:27-28
It is proper – that is, even though halachically it is more proper for those who eat to hear all of birkat ha-mazon from the mezammen, and he should discharge their obligations with his beracha, and they should not bless for themselves at all, in any case, because it is common, given our many sins, that those who eat are distracted and do not focus on the words of the mevarech at all, end up completely missing birkat ha-mazon, and actively fail to fulfill a positive Torah-level mitzva. Therefore, today it is more proper that those who eat should recite every word to themselves quietly along with mevarech, in order that they should recite it together, and thus it is called birkat ha-zimmun and fulfils what the verse says: “give greatness to God with me and let us exalt His name together,” for from this we derive birkat zimmun….The mezammen must recite in any event the first beracha aloud so that those eating hear him, and they say it quietly along with him word for word and just at the end of the beracha they should finish ahead of him so that they can answer amen [to the end] as Rema wrote…
[3] Berachot 46a
Until where is birkat ha-zimmun? Rav Nachman said: until “nevarech” and Rav Sheshet said: until “ha-zan.”
[4] This issue arises in discussion of one of three men eating together who pauses his eating in order to participate in the others' zimmun, where the question is how much he needs to hear before returning to his meal:
Shulchan Aruch OC 200:2
He needs to stop [eating] only until [the mezammen] says “Baruch she-achalnu mi-shelo…” and he goes back and finishes his meal without reciting a beracha first. Rema: Some say that he needs to stop [eating] until [the mezammen] says “ha-zan et ha-kol” and thus is the practice.Mishna Berura 183:28
Rather, the mezammen needs to recite at least the first beracha out loud so that those who eat can hear it, and they should say it quietly with him word by word, and only at the end of the beracha they should finish first in order to answer amen, as Rema wrote. See Magen Avraham, who is inclined to rule like Tashbetz who maintained that until “ha-zan” everyone needs to listen silently and have intention to discharge their obligation with the mezammen [and from there on, they should recite birkat ha-mazon quietly to themselves with the mezammen] because birkat ha-zimmun goes till there, but this is not our practice. In any case, it is good and proper, when he knows that those eating will have intent for his words, to do according to the Tashbetz; he should just notify them at the beginning that they should have intention to discharge their obligation and he will have intention to discharge their obligations, and specifically when all those listening understand Hebrew, for otherwise it is certainly better for them to recite the entire birkat ha-mazon themselves and not discharge their obligation with the mevarach [Eliya Rabba].
[5] Katuv Sham, Ra’avad Berachot 44a
Birkat zimmun, which is from the Torah…
[6] Chiddushei Ha-Ra’ah Berachot 45a
For we add birkat zimmun, and it is certainly rabbinic, and the verse is merely a mnemonic device…
[7] Kiryat Sefer Hilchot Berachot 5
We derive birkat zimmun from what is written “the Lord your God,” and it seems that this is birkat ha-zimmun with ten or more, when we mention God, for this is the simple meaning of the verse “the Lord your God”… Ten who ate together to satiety are not permitted to split up, because the obligation of zimmun falls upon them on a Torah level, as it is written “the Lord your God,” and this is a davar she-bikdusha and requires ten…
[8] Rosh Ha-shana 29a
Ahava son of R’ Zeira taught: for all berachot, even though he has [already] discharged [his obligation], he can discharge [the obligations of others], except for the beracha over bread and the beracha over wine, where if he has not discharged [his obligation], he can discharge [the obligations of others], and if he has discharged [his obligation], he cannot discharge [the obligations of others].
Rashi ad. loc.
Except for the beracha of bread and wine – and other berachot on fruits and scents…
[9] Berachot 45b
Abbaye said: We have a tradition: Two who ate as one – it is a mitzva to separate.
Rashi ad. loc.
It is a mitzva to separate – and for each person to recite the beracha individually, both for birkat ha-motzi and birkat ha-mazon.
[10] Rosh Berachot 6:33
One blesses for all of them. Yerushalmi: Rabbi Yehoshua ben Levi says: The mishna is the case of a berit mila with guests. That implies that a householder within his house, no. The explanation is that for a householder, since all the members of his household are drawn after him, they do not require reclining because they are all dependent upon him.
[11] Beit Yosef OC 167
…Anything without sitting does not constitute keva at all, and one person does not exempt his fellow.
Bei’ur Halacha 167:11, s.v. Ela im ken yashvu be-shulchan echad
Gera in his commentary wrote that, in the flow [of writing] from before, the author [of Shulchan Aruch] copied “one…” but we really don’t require one table or one tablecloth at all where they established in advance to eat together or a householder with members of his household, but all who sit and eat together, that is, where they are not scattered one here and one there, they join, as in siman 12, and not in accordance with Magen Avraham.
[12] Talmud Yerushalmi Berachot 7:1
Thus it is said, they are obligated to recite zimmun. Shemuel said: Here at the beginning, here at the end. Which is at the beginning and which is at the end? Two Amora'im: One said "they decided to eat," this is at the beginning. "They ate a ke-zayit," this is at the end. The other said: "They ate a ke’zayit," this is at the beginning. "They finished eating," this is at the end.
Rabbeinu Yona on Rif, Berachot 37a, Rif pagination
But it seems to my teacher the Rav to explain in a different way, that what they taught “three who sat down to eat are not permitted to separate” means that they sat down from the beginning with one hazmana and decided to eat together but did not recite ha-motzi. This comes to teach us that even though they did not yet begin to eat, and did not recite ha-motzi, they are not permitted to separate. Our [Babylonian] Talmud, which said “they sat” and not “they ate” reasons like the Amora who says in the Yerushalmi [they decided to eat, this is “at the beginning”]. And even though from the words of the Yerushalmi there is no determination to rule according to this language more than the other, since in our Talmud we see that he holds like this language, we rule according to it and say that even though they did not eat at all, for they have not yet recited ha-motzi, since they decided from the beginning to eat together, even if they ate afterwards each one on his own, they are not permitted to separate and recite birkat ha-mazon each one for himself, but they need to recite it together in order to exempt themselves from zimmun….Since they accepted upon themselves to perform a mitzva, they need to fulfill it…
[13] Rosh Berachot 7:29
Gemara; What does this teach us? We have already learned this once in a mishna: Three who ate as one are obligated in zimmun. This comes to teach us that what R’ Abba said Shemuel said: Three who sat down to eat are not permitted to separate, meaning that they sat down to eat and recited birkat ha-motzi and have not yet eaten the measure for a beracha, are not permitted to separate, and this is a stringency that our sages enacted in the matter.
[14] Mishna Berura 193:19
At the end of eating – Their obligation of zimmun takes effect through their eating together at the end, and we understand from this that if they also did not finish eating together, as when one person came to eat with two after they had already started eating, and they also did not finish their meal at the same time, those who finished earlier are permitted to recite birkat ha-mazon on their own, since we at least require either beginning or finishing together, and in any case if they delayed after their eating and did not recite birkat ha-mazon until the third person also finished eating, they are required to recite zimmun and are not permitted to separate, and even though they did not finish together, as long as if someone brought them something they would be able to eat from it, we consider it as if they finished together, as is expounded in siman 197, see there.
[15] Berachot 45b
Three who ate as one – one stops [eating] for two [to recite birkat ha-mazon], and two do not stop for one.
[16] דאמר רב הונא: שלשה שבאו משלש חבורות - אינן רשאין ליחלק. אמר רב חסדא: והוא - שבאו משלש חבורות של שלשה בני אדם.  אמר רבא: ולא אמרן - אלא דלא אקדימו הנך ואזמון עלייהו בדוכתייהו, אבל אזמון עלייהו בדוכתייהו - פרח זימון מינייהו. 
Berachot 50a-b
As Rav Huna said: Three who came from three chavurot – they are not permitted to separate. Rav Chisda said: This is when they came from three chavurot of three people. Rava said: And we say this only if they did not first include them in the zimmun in their place, but if they included them in the zimmun in their place, the [obligation of] zimmun has left them.
[17] See also here:
Kitzur Piskei Ha-Rosh Berachot 7:4
Women recite zimmun for themselves and are obligated to do so, and bondsmen recite zimmun for themselves, and women and bondsmen do not join together, and it is puzzling that women now do not have the custom to recite zimmun.
This view seems to be shared by many others, including Rabbeinu Yona, Rokeach, and Rambam:
Rabbeinu Yona on Rif Berachot 33a, Rif pagination
It seems to my teacher the Rav that they are obligated to recite zimmun because they ultimately resolve in the gemara: "it is different there [in that case of three women reciting zimmun], because there are [three distinct] minds," and it seems to say that even though they are women, since they are three, the law is that they should recite zimmun, for there are three minds. But with two men, where there are not three minds, no. And since the matter ultimately depends on [the presence of] minds, the simple meaning is that they are obligated to recite zimmun when they are three.
Sefer Ha-Roke’ach Hilchot Seuda 333
Women and bondsmen recite zimmun for themselves and are obligated in zimmun.
Rambam Hilchot Berachot 5:7
Women and bondsmen and minors are not included in a [freemen’s] zimmun, but they recite zimmun for themselves, and there should not be a chavura of women and bondsmen and minors because of licentiousness, but women recite zimmun for themselves…
[18] Aruch Ha-shulchan OC 199:2
…We have never heard of women reciting zimmun for themselves…
[19]Rav Ari Zivotofsky, “What's the Truth about Women's Zimmun,” Jewish Action, Fall 1999. https://jewishaction.com/religion/whats-truth-aboutwomens-zimun/
Rav Dovid Cohen, Letter to Jewish Action, winter 2000.
…There are two worlds: halacha and halacha lema'aseh. It is my halachic opinion that women's minyanim…and the like, are prohibited by the Torah because they are consequences of the feminist movement. I would not answer even as an "outsider" in front of the women, since this could be construed as giving assent to [feminist] actions that I find objectionable.
[20] https://www.etzion.org.il/en/shiur-zimun
[21]  Ritva, who maintains that women's obligation is on a Torah level, writes that a woman may lead a man in zimmun:
Ritva Hilchot Berachot 7:2
Women are obligated in birkat ha-mazon on a Torah level and therefore a woman can recite birkat ha-mazon through zimmun for a man.
[22] Rav Wosner adds a justification for men who leave the Shabbat meal before birkat ha-mazon to join the Rebbe’s tisch, leaving the women at home without a zimmun. He relies on an otherwise rejected opinion:
Responsa Shevet Ha-levi I:38
That which you asked, a question to a scholar, that since it is established in SA 199 that women with men are obligated in zimmun and discharge their obligation through the men, if so, how do we justify the custom of chassidim and people of deeds, who go after the meal at home to the tisch of their rabbi and remove in this way the obligation of zimmun from the women, upon whom it has already fallen?.... It seems to me that they rely on the opinion of Bach, in Magen Avraham 200:2, who wrote according to the approach of Rav Hai Ga’on, that before the end of the meal, even if they were together at the beginning of the meal, one is still permitted to depart, and 183:4 applies when they finished their meal in that place, and if so, here in our case, where they go out before the end of the meal, and finish their meal at their rabbi’s tisch, we have the iron pillars of Bach and Magen Avraham upon whom to rely. As for the halacha [in general] for men, the great later halachic authorities rejected the words of Bach from halacha…
[23] Sha’ar Ha-tziyyun 199:9
…Since they [women] became obligated in zimmun because they ate with a chavura of three men and the obligation certainly falls on them as well, as Levush wrote, even after they separated from them, their [women's] obligation did not go away, and they are still obligated in zimmun and it is not optional…For we cannot force them to sit specifically in one chavura with men, and especially according to Gera who ruled that women are obligated to recite zimmun for themselves, certainly they would not lose anything by separating.