Question: A congregation includes many working members with a fixed lunch break (e.g., 1:00–1:30 PM). The mosque is only minutes away, prays Zuhr at 1:10 PM. In winter it gets earlier earlier, while the lunch break remains fixed. Is it permissible for the mosque to keep the Zuhr time fixed at 1:10 PM year-round and what should a working congregant do if this is not accommodated by our musjid? We had an imam that would do the Friday khutba sometimes before the time. So can this be done for working people regularly for Zuhr?

Answer:
The time for Zuhr begins once the sun passes its zenith and lasts until the time for Asr enters. Rasool ﷺ said: The time of the Zuhr prayer is when the sun passes the meridian… It lasts until the time of the ‘Asr prayer. (Sahih Muslim)
This hadith establishes the outer boundaries of Zuhr’s valid time — from zenith until Asr — and does not require praying at the earliest possible moment within that window. Delaying Zuhr somewhat within its valid time for the legitimate benefit to the congregation does not conflict with this religion. As a matter of fact, it is sunnah — as per hadith to delay the Zuhr, more so in hot seasons. Generally this is not done, so as to not disturb the schedule of thouse working.
Having a fixed congregational time particularly for Zuhr is best, moreso for a working crowd. So long as the time remains within the boundaries outlined above — such as 1:10 PM —  provided that this time reliably falls after true zenith on every day of the year, including the shortest days of winter, when zenith occurs earliest. Since a fixed time serves a real and recognized benefit (enabling working congregants to attend consistently, rather than needing with the time) and does not violate the boundaries,  this should be given preference.).
If the congregation requests a seasonal adjustment and it is not granted, a working congregant bound by a fixed schedule has two valid options:
Pray individually at the mosque or elsewhere, more so if attending the congregational prayer is not possible due to a genuine ongoing constraint (such as a fixed work schedule). A person prevented from congregational prayer by a legitimate excuse is not deprived of full reward for their sincere effort to fulfill the obligation on time.
Form an informal congregation with others facing the same constraint, provided this takes place away from the main prayer hall, does not conflict with the Masjids operational policies and does not create disturbance or disorder within the institution. This Zuhr prayer must be done outside the hours of the main prayer session. Congregational prayer performed under such circumstances remains valid and rewarded as such.

Allah Certainly Knows Best.