ZoneProperty() is a function, and as such, you cannot treat it as an lvalue (meaning you can't assign to it with "="). I think you want to use the CreateZone() function when loading information from a file.
Out of curiousity, why can't an isometric tile-based RPG use the division solution I outlined above? It would be a substantially simpler approach if it could be made to work for you.
Out of curiousity, why can't an isometric tile-based RPG use the division solution I outlined above? It would be a substantially simpler approach if it could be made to work for you.