I still remember advertising for Zool from Gremlin and also I am thinking of Zool as an Amiga game, no DOS BS ! So I suppose, if the arcade port ever happened, that would be on M68000 at ~ 8 MHz and Yamaha sound chip or something similar to that. However, beside the fact I was (those years) a big fan of Amiga games, I think that Zool was popular only in UK and was overrated too. So the arcade machine (if ever happened) should be found exactly in UK. Also that game was far away from ROTR (technically speaking) and I think the eventual ROM should be ~ 2 MBs - so no need of HD.
P.S. This is just my AMATEURISH point of view, so sorry if I told something wrong/stupid