One thing of note, is that the original version of the game was all to take place above ground. Thus all locations from the final version appear on a single map. It was only late in the design process when it was decided to split the region into aboveground and underground sections. Unfortunately, the only maps I seem to have all of are the Version 2 ones.

Version 0 are the prototype versions
Version 1 is one of the early versions in the design documents
Version 2 is one of the revised versions (the Hidden Passage replaced with the Dwarven Mines mainly)

A The Valley of the Vultures Version 1
Version 2
B West Shanbar Version 2
C East Shanbar & Witch's Hut Version 0
Version 2

In Version 2, Map G (Hut) was combined into Map C (Shanbar)
D Forest of the Spirits & Waterfall Version 2
E Mountain Pass Version 2
F Snoot's Farm & Pugney Ranch & Vultures Pits Version 2
G [Witch's Hut] Version 0
Version 1

In Version 2, Map G (Hut) was combined into Map C
H Whispering Woods & Ferryman's Isle Version 1A
Version 2
I Bel Naire Temple Version 0
Version 1
Version 2
J Dwarven Mines & Ancient Ruins Version 0A
Version 1A
Version 1B
Version 2
Originally Hidden Passage instead of Dwarven Mines
Originally Hidden Passage instead of Dwarven Mines
K Cliffs of Depression Version 2
L Citadel of Zork Version 2
M Bridge & Old Mill Version 2
N [not available] Map N was a poor placeholder interface diagram
O Troll Caverns Version 2

These two maps above were made late in the production process, showing some early ideas of what was to be aboveground and what was to be underground:

    Valley of the Vultures:
                Aboveground Map
                Underground Map