The big reveal of Zoom’s identity was made – he is apparently another version of Jay Garrick. Apart from Zoom’s identity, the identity of the mysterious man in the Iron mask who is caged in Zoom’s lair also became quite clear. He is also Jay Garrick but the Earth-1 version of it. He is the original doppelganger of Earth-2 Jay Garrick on Earth-1. When Jay Garrick showed Caitlin his doppelganger on Earth-1, he was deceiving her as he was actually Zoom or Hunter Zolomon whereas the original doppelganger is taken and caged in Zoom’s lair.
Hunter Zolomon is a dark version of Jay Garrick with a blue lightning/ speed force. He acquired speed-force as a result of particle accelerator explosion, experimented with sizeable quantities of the Velocity-9 drug, got addicted to it which had a negative impact on his mind. He could also be a Cobalt Blue/Malcolm Thawne type of character i.e actual physical twin before the explosion of particle accelerator.
In the next episode, the Flash will be taking the fight to Zoom and we will understand the real motives of why Zoom is such an evil. It’s pretty clear that his story is akin to that of Avery from Making a Murderer series. Hunter Zolomon was an innocent child who was sent to foster care, and then thrown into Earth-2 prison system, subjected to torture, and finally became a convicted serial killer. He is grown up to be a scientist who formulated velocity-9 drug and used it for his sinister motives. The question is how will the Zoom’s storyline be resolved?
Zoom/Hunter Zolomon is a speedster like Barry Allen without meeting good people in his childhood and good things happen to him. Can Zoom be fixed or redeemed somehow? Can Barry go back in time, change his past so that something good happen to him? But we know there is a huge risk if one tries to distort timeline, in the last episode we saw time wraiths chasing Flash as he is time-travelling. Should Zoom end up like Trajectory and turn into pure energy i.e absorbed into the speed force due to over-consumption of velocity-9? A lot will depend on who the mysterious man in the iron mask really is? Let’s wait and see what happens.