So, ZOOM looks like the person that has claimed to be Jay Garrick.
Yet we have the man in the mask who is likely the real Jay.
On Earth 1 "Jay's" counter part is named Hunter Zolomon thanks to being adopted.....hmmmm
ZOOM is looking more likely to be Hunter Zolomon and if they are sticking to the comics, then his power is to warp time for himself to simulate super speed. But suppose he can go one further and make a temporal counter part of himself, minus speed powers and thus needs the Velocity serum. This counterpart is instructed to get to Earth 1 and claim to be Jay Garrick while the real Jay is imprisoned. The mask prevents him from speaking, his face cant be seen and his speed powers are blocked by it.
Or ZOOM doesn't need portals to dimension jump and has pulled a counterpart from another Earth to pose as the Earth 2 Flash.
Or the "Jay" we have met so far is THE RIVAL aka Earth 2 Reverse Flash. he has always needed the Velocity serum, Jay does not. Why does he look like ZOOM? Good question, perhaps the question should be why does ZOOM look like him? Was there some face stealing similar to what RF did to Wells in Season 1?
We shall see in a few weeks as the show is on hiatus now.
The Flash's Earth-3 counterpart?
Johnny Quick of the Crime Syndicate?