Use this button to remove existing zoneTypes. You may not remove the last zoneType, as it makes no sense to do so.
When you remove zoneTypes the existing population may need adjustment as it may contain shapes of zoneTypes that have been deleted. When you delete a zoneType, any shape of the deleted type in any design will be randomly assigned from the still-existing zoneTypes. That means that if you have seven zoneTypes, delete all but one, and then add the other six back, your population will contain shapes only of the first zoneType. (Of course the others may evolve back in.)