I don't have any experience with zac's but the hv circuit looks pretty similar to other manufacturers around that time.

Did you check the 1a fuse at F1? Make sure to pull it out and check it with a meter. I'd also check the bridge rectifier for the circuit, marked P1 on the schematic. If both those check good, I'd check the HV transistors, TR1, TR2, and TR3, zener diodes DZ1 and DZ2, and diodes D1, D2, and D3 (D1 is cut off on the schematic, unfortunately so not sure what type it is) . Also check for for any other burned up resistors/diodes/transistors in the hv section. There's a big 100uf/350v electrolytic cap at c1 that's probably due to the be replaced, as well. If all those parts are original, it might be worth simply rebuilding the hv section.

Hopefully someone with more experience with these games will chime in, but maybe this info will help get the ball rolling in the meantime.

Here's a shot of the hv section from the schematics i downloaded from ipdb.org:

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