Hi guys I'm going to tell you who I think is Zoom. Let's start!
1. Henry Allen from E-2
He is my #1 suspect about this. You probably wonder ,,Why''?!
Well for start he gets out of prison in which he was about 15 years and suddenly he decides to heat the road! So my theory is that Zoom ( Henry from Earth-2, maybe) kidnapped or killed Henry from Earth-1 and continued acting to be Earth's 1 Henry. That's why started acting strange in last couple of episodes.
2. Wally West a.k.a. Kid Flash from E-2
Adding Wally into the show would be awesome and even better as a villain. For those who didn't read comics or watched Young Justice he is Joe's son who got powers the same way like Barry.
3. Black Flash also known as Black Racer
He is manifestation of Speed force it self. He looks a lot like Zoom and both of them are killing speedsters and steeling their speed. He appears in Smallville TV show or comic book I'm not sure, but I am sure that he is creepy!
4. Barry Allen from E-2
This is would be the most obvious solution and I don't think that they are going to chose it. Because that would be lame ( that is my opinion) and I mean imagine Barry trying to figure it out and then Cisco vibes out why Barry turned evil... But it's possible.
5. Hunter Zolomon
Maybe they'll chose him because he is original Zoom from comic books. In that case they'll probably have same background story.
So adding new characters like Wally, Hunter and Black flash would be so much cool. And what do you guys think who is Zoom? Comment below!