For those units where ZOR isn't mentioned at all I had in mind you'd be able to recruit them anywhere. Generally, I try to make all militia recruitable almost anywhere, whereas the better troops are often, but not always, restricted. It depends on the recruiting system. The Byzantines historically got problems with losing recruitment areas so I think they should have problems with it in the mod. If a faction almost only uses militia or other troops that require little training they should be able to train all their troops anywhere IMO. Still, they'll need some time before they can train their troops as I'll try to make all troop buildings incompatible with each other if possible, so you have to tear down an enemy's buildings and can't retrain your troops in newly conquered settlements. So for non-ZOR units you can recruit them anywhere, but only after some time which you can see as the time needed for loyalty in the settlement to increase.