EQ Zone Viewer is a third party utility that allows you to... wait for it... view EQ zones
You don't use it with Everquest, but you can load up zones offline and walk around in them, clip through all, raise yourself far above the ground for an aerial view of the zone, etc. It does not display mobs of any sort (monsters, quest NPCs, merchants, etc). As I said, its spoiler potentials are fairly limited since you usually want to know that there's five zombies in a room waiting to jump you, not that it has a bookcase and a table. Really, it's about the same as looking at a zone map on
EQ Atlas except you're walking around through it, not just looking at it.
On the other hand, it's kind of fun for getting a sense of scale and zone construction. Sebilis was fun to look at how twisty and turny the tunnels and passages are as you get deeper and deeper in. The Miragul LDoN dungeons impressed me with how frickin' huge they are, even if it mainly is one long tunnel.