Earth-2 Barry can be scratched off as he was always with Wells, Cisco, E2 Iris, and Killer Frost.
I'm also going to go ahead and eliminate E2 Henry. He was a moonshot and was chosen for the potential drama of The Flash having to fight his dad's doppelganger.
I'm not sure about Earth-2 Wally because we never saw him and neither Iris or Joe mentioned him, so it's questionable if Wally even exists on that Earth. He's provisionally eliminated unless new evidence surfaces of his existence.
This brings us to Jay Garrick and his Earth-1 counterpart, Hunter Zolomon. As I mentioned in the first Zoom post, Hunter Zolomon is Zoom in the comics and on one hand that can't be overlooked, but on the other hand, it feels so much like a red herring. That might be the writers' intention, to make Zolomon look like a red herring in order to throw off the comic fans and people who look characters up on Google.
Then there's Jay. Jay, Jay, Jay. He was a bit shady in "Escape from Earth-2" and there were a lot of hints that he could somehow be Zoom. In the previous episode, "Welcome to Earth-2", Jay confessed to Caitlin that Zoom didn't steal his speed like he originally told Team Flash, but rather he'd lost it from taking Velocity 6 to boost his speed. That raised some red flags with me because if he lied about that, then what else is he hiding? Then, in "Escape from Earth-2", he uses the newly created Velocity 9 to restore his speed long enough to save civilians from a building Geomancer collapsed. Claiming exhaustion, he goes to take a rest somewhere in S.T.A.R. Labs, but when Geomancer shows up and attacks Caitlin and Iris, he's nowhere to be found. This is despite Geomancer wrecking the place with his powers. Plus, just before the attack, Caitlin called for him over the Lab's intercom, but he still didn't show up until after Caitlin dealt with Geomancer herself.
Let me elaborate. Throughout the episode, the guy taps on the transparent wall of his cell over and over again. Jesse thinks that it's meaningless, but Barry realizes that it's the same form of code used by prisoners of war and together, they decipher what the helmeted man is telling them and it's one name: Jay. Barry thinks he's asking about Jay and tells him that Jay's alive, but that only elicits a negative reaction from the helmeted man, almost as if he's trying to tell them something about Jay Garrick, but they're not understanding. And it might be nothing at all, but they also give us a closeup of the side of this guy's head and you can see some of his hair and well, it's the same color as Jay's.
Hmm. So who is this guy? We never see him without the helmet because Flash, Jesse, and their rescuers (sans Killer Frost, who stays behind to hold off Zoom) are forced to flee for their lives before Flash can free him too.
In The Man in the Iron Mask by Alexander Dumas, the eponymous man is the identical brother of King Louis XIV, so what if there's something similar at work here too? Not an identical twin, but a counterpart, a doppelganger. What if Zoom isn't from Earth-2, but merely traveled there from yet another Earth. After all, Zoom knew about Earth-1 and Barry Allen before the breaches, so it stands to reason that he knew about the larger multiverse too. With that in mind, who's to say that the Jay Garrick who joined Team Flash is from Earth-2? The helmeted man could be Earth-2 Jay and Zoom could be from I don't know, Earth-3 or something. Maybe it is Hunter Zolomon from Earth-1 or a Zolomon from another Earth.
There are problems with this theory, however. First, Geomancer's attack on S.T.A.R. Labs damaged the speed cannon and destabilizing the sole remaining breach to Earth-2. Jay was there during this mini-crisis and helped fix the problem while in the presence of Caitlin, Iris, and Joe. Second, at the very end of the episode while Team Flash is celebrating the rescue of Jesse, their return to Earth-1, and the closing of the final breach, Zoom shoves his hand through Jay's chest (who, god knows why, was standing right in front of the breach) and yanks him through before it closes.
So yeah, problems. My only solution that is that Team Flash's Jay is from Earth-2 and the helmeted man is a Jay from another Earth. Zoom could still be Zolomon because we haven't seen him since "The Reverse-Flash Returns". He could also still be a Jay from an alternate Earth.
Definitely more questions than answers, but the mystery of Zoom's identity is certainly keeping us coming back every week for more clues and answers.
Who do you think Zoom is? Tell me down in the comments.