Question Summary:
Second Jamā῾t in a Masjid

Question Detail:

Is it permissible to perform a 2nd Jamā῾t in a Masjid where an Imām is defined by the elders?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh. 
In a Masjid where five daily prayers are taking place with Adhan and Iqāmah, it is Makruh Tahrimi (prohibitively disliked) to conduct a second congregation, since it decreases the importance of the official congregation.  
If you wish to pray in congregation, it may be conduct outside the Masjid area. Otherwise, the Salāh should be preformed individually. [1]
And Allah Ta’āla Knows Best
Mufti Zaid Mohammed Shelia,
Student Darul Iftaa
USA 
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net