You can only have one coordinator in a Zigbee network, so you are looking at two separate networks.
Only one of those can be ZHA, but ZHA and Z2M can run at the same time.
Each of your devices has to belong to one Zigbee network or the other, no crossover.
You can only have one instance of Home Assistant on your LAN, so if you’re going to run ZHA and Z2M, both coordinators would be on the same PC.
Zigbee is not a good choice if you want to cross a distance between two buildings - the signal is very weak.
There’s a big Zigbee section in the “Cookbook”: