If 2 chaburos are eating in same house and they only see eachother through a mirror can they be mitztaref for a zimun?
The two chaburos are not mitztaref to a zimun. Although they can technically see each other, but they are not actually seeing each other, but only a picture of the other chabura- similar to seeing them on a video.
Kesiva Vchasima Tova
Kaf Hachayim 195-1 in the name of Pesach Hadevir, Birkas Shem 4-7, Poskim.