For a game with large landscape, many puzzles, and a harsh inventory limit, it’s essential to have a base of operations: a place to stash everything. One of my stopping points in Zork is that it’s been hard to find one due to the thief (who will keep treasures, and take non-treasures and drop them off at random spots on the map).
A good base here needed, preferably:
a.) To be fairly central to the map
b.) To be a place avoided by the thief
c.) To have its own source of light, so I can give the (time-limited) battery powered lantern a rest while I rummage through items and decide my next move
d.) Be reasonably close to an egress to the surface, to make it easier to start filling the trophy case with treasures
I originally tried the Flood Control Dam #3, because it seemed to fit conditions a, b, and c and marginally d (it’s five rooms away from the Cellar and exit — once the trophy case has at least one treasure the trapdoor stays open) but I discovered that the thief does show up, he just doesn’t show his face; items in the room just start disappearing one by one.
After fussing about some more, I noticed the Temple was also well lit, and lo (peeking at David Cornelson’s map to see if I missed anything on my map) there’s a very good source for exit to the surface and the thief also avoids the temple.
So my progress has accelerated, although strangely I haven’t really solved much more; just I’ve been able to put together all the parts I’ve solved during individual runs on a continuous run.
Renga in Blue 
The safe place is where you’d expect it to be and there’s a trick to preventing the thief from taking things out of the trophy case. I will leave you with that hint.
Also – if anyone finds any flaws with my map, please let me know. Of course then I’ll have to go dig up the Visio version, but I’d like to make sure it’s accurate.
I don’t know if Dungeon is different, but my maze map (with the cyclops room/grating added) is slightly different than yours. I’ll post it up once I get it rendered in Trizbort.
I was playing mainframe Zork the other day & discovered I could kill the thief with very little trouble at slightly more than 300 points.
I always found the Dam Base to be a good place to keep things in Zork I.
I tested out and managed to kill the thief with only around 190. (Which is possible getting only the fairly-easy-to-grab treasures.)
I’m just dumping my stuff in the living room. The thief never stole anything, and I’ve killed him off.