The zone-file is the most important file you'll make since it decides what loads where, which mob uses which item, and who follows whom. And now there are special new zone commands that allow you to remove mobs, items, and have diurnal/nocturnal mobs as well.
Important Notes on making the .zon File:
1) Whatever you do, make SURE you comment your zone file. You will see what I mean in the example below, but in brief, make sure that after EVERY load you put in, write a comment after it to tell us (The Makers) what you are loading there.
2) Under NO circumstances are you to use any item or mob from another zone in your zone!!! If you want to do this, then copy the mob or item into your own .mob or .obj, and renumber it so it's in your .obj range. This is a MUST.
3) Take care in assigning Temperature to the zone. Freezing, Heatstroke and boiling all do damage every tic to a player. Do NOT use those without a good reason. (The Arctic tundra would be freezing for example). Also realize that strong winds can be very annoying for players.