It's not fukking Wally
Dude in the mask had blonde hair, they showed the back of his neck...
Honestly, this Hunter Zolomon character is who Zoom is in the comics (or one version of him I guess) so that's where the theories of a twin/doppelgänger and E2 vs. E1's twins/doppelgängers are coming into play.
Now I really don't know shyt and I'm guessing this is what the Flashes show runners want.
All I know is that dude in the iron mask spelled out JAY and flipped out when E2 Jay Garrick's name was mentioned, which makes me believe that either he is actually E2 Jay or E2 Jay is Zoom somehow.
Also, Fake-Jay said he never found his doppelgänger on earth 1... Which could be a lie since dude has been shady af lately. Could've been a ploy to get Caitlan to develop the Velocity 9 for Zoom all along, since Wells couldn't do it right. It's no coincidence that Jay goes missing and that Jay got sucked back to E2.. Probably with Velocity 9 still in his system or with a batch of serum stolen from the lab.
Also, man in the iron mask was in a cage like Barry's.. Which makes me think he really is E2 Jay Garrick with stolen speed and the other Jay is someone else who tried to develop speed using velocity serums...
But i dont know, this shyt is confusing