I don't think there is a "simple" way of doing this. You can clear out all your objects and graphics and load in the new stuff for the new zone.
Another option is to have a different .exe file for each zone. Then when you "open a door" to another zone, you save all the pertenant information to a text file (encoded if you like), run the next zone's .exe and finally end itself. Then the new zone executes and loads the text file data. This would be one way of handling Very Large zones.
"Droids don't rip your arms off when they lose." -H. Solo
REALITY II