OK, so the parent set is an earlier release, right?
From what I'm seeing, MAME doesn't use early versions as parent sets (examples here), unless they're the only one available (like barata).
Also, in most cases the latest revisions of a game are used as parent sets - excluding obviously unofficial releases (hacks, bootlegs, Phoenix editions, etc).
MAME seems very consistent with these rules, so I think exzisusa should be changed as the parent set, if it's confirmed as later than exzisus.
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