Until when is it permissible to pray in congregation in the university prayer hall after the Dhuhr Adhan?

The Dhuhr prayer is preferred to be performed in one congregation, based on the Prophet's (peace be upon him) saying: "A man's prayer with another man is purer than his prayer alone, and the prayer of two men is purer than his prayer with one man, and what is more numerous is more beloved to Allah the Almighty." If this is not possible, it is permissible for one congregation to pray, followed by another congregation, as long as the prayer time remains. It is not permissible to delay the prayer beyond its prescribed time.