If you haven't seen the latest episodes of the Flash, be careful this post may contain spoilers from episod 13 and 14 of Season 2.
In the latest episode of The Flash, 'Escape From Earth-2', we saw a man with an iron mask, that was talking to Barry and Jesse by tapping on the cell glass. He was tapping the three letters J...A...Y. Which is a referens to Jay Garrick AKA the golden age Flash.
The man in the iron mask is the real Earth-2 Jay Garrick that Zoom has capture sometime between when Earth-2s particle accelerator went wrong and when the Jay Garrick we know came to Earth-1 through the singularity.
I think that Zoom isn't from Earth-2, I think he is from another Earth, like Earth 52 or something like that. But now he is stucked on Earth-2 and the only way for him to get back to his Earth is to have so much speed that he can travel from one Earth to another. And that is why he needs Barry's speed. But it can also be that he just want to be the fastest and the only speedster. UPDATE: (and another thing that I forgot is that Harrison Wells created Zoom so he can't be from another Earth.)
The Jay Garrick we have seen over the most of season 2 is no one other than Edward Clariss AKA golden age Reverse Flash/The Rival.
Who was ordered to take on the mantel of Jay Garrick in order to trick Barry to let him help him to get faster. So Zoom later could take Barry's speed. In the comics he also haft to take the formula called Velocity 9 in order to run as fast as the speed of light. He later became so fast that he was sucked in to the speed force.
But in the end of episode 14 this happened:
"Jay Garrick" was draged back to Earth-2 from Earth-1 through the last remaining breach by Zoom in the last second before it closed. But I don't think that "Jay Garrick" is dead. Because if you don't see a body of the person, it is a chance that the person is still alive.
But that is just my theory how things is about "Jay Garrick", Zoom and the man in the iron mask.
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See You Later Alligator!