Think if both packs to stby c, they will both suppy cool temp air.
Zone contoller with need to keep zone valves more open that normal so as to supply suitable temps in zone.
In the above case, it may be that during flt zones may get to cold because volume of trim zone air will not raise duct temp enough.
If the above case and if both packs will only run stby c, may be switch off one pack to reduce cool air supply, think other pack will then supply 120% flow, but still cutting total flow by 80% and would guess the zone temps will be ok then may be.
Is this the question you asking.......???