Be warned! Spoilers are ahead for this season and possible future episodes of The Flash.
After watching the second half of season 6 premiere of The Flash, and running down the list of possible people that Zoom could be, it hit me after watching the glimpses that Barry was seeing on his way to Earth-2. It finally hit me!
Zoom must be the Earth-2 version of Henry Allen, Barry's dad. I don't have any proof to validate this claim and this is pure speculation, but the eyes. The eyes are what is leading me to this conclusion. They are out clear as day.
The similarities between the eyes of Henry and Zoom are too much to ignore and let pass.
Think about it. Everything in Earth-2 is the opposite of the Earth Flash is on. The love Henry has for Barry on his Earth is immeasurable, and the same can be said for the hate Zoom has for The Flash.
Zoom's obsession with being faster and more powerful has probably lead him to not see his son in Barry. Just like Dr. Wells from Earth-2 said to Barry after the attack that killed the Earth-2 Joe.
These people, Barry, are mere reflections, and as far as your life is concerned, they don't exist.
This could be the same approach that Zoom might be taking in regards to Barry being The Flash on this Earth.
The eyes. It all started with the eyes. The lighting on the images I could get was not so great, but when seeing this pictures in better quality, you will see that they have the same color eyes.
As I said before, this is all unproven and pure speculation, but it's hard to ignore.