Agree with Jeremiah, I was considering you already had simplified the model as much as possible, on this matter it is recommended that you use simple shaped zones, with less surfaces. I did only 4 shopping center models where I used to work and the first step was group all the similar projected zones (normal stores grouped, big stores that use their own HVAC grouped, service areas grouped...) and make the model zones more "squared".
As long as you do not change the conditioned or unconditioned zones frontiers with the outside and between conditioned/unconditioned zones, the internal contacts and shapes of the zones will do little to no difference on final simulation. Similarly, if you do not use automated lights or other "sun dependant" controls, it helps to make simpler fenestrations (group all the subsurfaces of a zone in one with equivalent area, as long as they have same orientation)
I attached a zonning example (of this shopping
http://bosquedosipes.com/, being built here "
Campo Grande - MS, 79062-200, República Federativa do Brasil" , this address can be found on googlemaps) that I did in the past, it is in E+6 but may help, also not the final model. The final model with all the systems and zones took some 40minutes on timestep 8, calibration with timestep 1 took less than 10min for annual sim. I usually use timestep up to 15, but mostly 4 to 10, not sure the results with 30 or 60 are better.
Leandro