He was the stepbrother and successor of Nahshon ben Zadok, and has become known especially through the reply which he made to the inquiry of the Kairwanites regarding Eldad ha-Dani.
This responsum, which appeared in part in the first edition of the Shalshelet ha-Ḳabbalah (Venice, 1480), was republished as completely as possible by A. Epstein in Vienna in his Eldad ha-Dani.
It embraces nine points and concludes with an apology for Eldad's forgetfulness.
According to Epstein, only one other responsum by Ẓemaḥ has been published; it is given in the Constantinople edition of the Pardes, and ends with the same words as does the first-mentioned responsum: לנטות ימין ושמאל.
Weiss, however, ascribes to this gaon also the authorship of responsa in Sha'arei Tzedek (iv., No.