Answered by Shaykh Faraz Rabbani
Second Congregations. RE: Would it be permissible to have two different prayer congregations in the same prayer hall for the same prayer? How about in a masjid?
Walaikum assalam wa rahmatullah,
The fatwa of most of the late scholars is that both are permitted.
The transmitted position of Abu Hanifa is that doing so in the mosque is prohibitively disliked. This is the position followed by the top Indian scholars of the last 120 years, and is the position I personally follow.
See answer below.