Is it permissible for a follower to join the Imam in the Friday prayer (Jumu'ah) if the Imam begins the prayer before the zenith (Zawāl)?

Primary text

It is not permissible for the follower to join the Imam in Jumu'ah if the follower only catches a portion of the prayer and the Imam began before Zawāl. For the follower, that prayer is considered the noon prayer (Dhuhr), and Dhuhr prayer is not permitted before Zawāl, similar to the ruling regarding the reason for attending Jumu'ah. If one enters upon the Imam in this situation, the prayer counts as a voluntary (nafl) prayer for the follower and is not sufficient for fulfilling the obligatory Dhuhr prayer.