EQ Zone Viewer was a different program than ShowEQ. ShowEQ provided things like current mob locations, spawn tables, etc and was basically a cheating program. [Edit: My mistake there, I thought you were confusing them. You weren't; I was confused about you instead
EQ Zone Viewer read the zone files on your hard drive and let you move around the zone. It didn't show anything stored server-side (mobs, doors, etc) and didn't connect to the server at all -- you could run it with your computer offline. It may have still been against the EULA but it wasn't much of a cheating tool since it only showed the zone geography and nothing else.
I know EQ Zone Viewer worked as late as LDoN; I looked at some of the dungeons and they were impressively enormous when panned out. I'm not sure if I still own it though; I think it got dumped at some point when I took EQ off my hard drive. Edited, Aug 24th 2012 10:01am by Jophiel