When trying to customize the game map, if imports slots and exports are outside a zone, the game won’t be able to initialize and crash. I saw the message “failed to initialize” in that case.
I think that when a zone is deleted, every import slot and exports inside it should be deleted as well.
Using map customization, if you make a zone without any import slot nor export, if you save it the game will crash. Worse on it, i encountered the message “Unknown Building Zone Type:…src\SIM_Mission.cpp 220” , which happens every time after i launch the game and click on “new game”. The only way i found to solve this is to reinstall the game.