Any zone with over 60 ohms tell the wiring is faulty. If there are 3 commons all connected in the field my guess with out being there 1 of them must be bad at some point causing the 100+ohms.
Last week I was working on an old system that thad 128 ohms for the first 4 valves I was working on, turned out that the splice on the old wire was a partial connection.. It was that wire that was corroded and when you spliced it in the nut broke.. Not cutting the entire connection, keeping continuity but just poorly..The splice box @ clock was non waterproof nuts inside an old 600 body duct taped direct buried into ground not a few feet from the indoor clock kept outside..
poor common connection, did you do a short to earth?
Thats my guess..