What is the ruling on communal remembrance (dhikr) on the two days of Eid in the mosque, where the worshippers repeat fixed phrases from the Sunnah after a specific person?

If the dhikr (remembrance of Allah) that the Imam recites with the worshippers on the two Eids is the takbir (Allahu Akbar), then there is no harm in that. It is recommended to proclaim the takbir collectively and individually on the nights of both Eids, everywhere. On Eid al-Fitr, the takbir begins from sunset on the night of Eid and ends with the Imam coming out for the Eid prayer. As for Eid al-Adha, the unrestricted takbir begins from the sighting of thejhilal (crescent moon) of Dhul-Hijjah until the last of the Days of Tashreeq, and the restricted takbir begins from the dawn of the Day of Arafah until the afternoon of the last of the Days of Tashreeq. There are preferred formulas for the takbir, and the matter is flexible.