After half-a-season's worth of tension, the identity of Zoom was revealed on Season 2 Episode 15 of "The Flash", titled "King Shark." However, before exposing anything more than the face behind the mask, "The Flash" went on a break, and will be returning only Tuesday, March 22.
A few episodes back, fans had seen Hunter Zolomon of Earth-1, when Jay Garrick (Teddy Sears) showed him to Caitlyn (Danielle Panabaker). They were searching for Jay of Earth-1, but realised that the only person on Central City that looks similar to The Flash of Earth-2 is Hunter. Assuming no rules are written in stone, they figured Jay's doppelganger is named Hunter.
However, when Zoom removed his mask and revealed that he is a Jay Garrick look-alike, things became muddled for a while before it was clarified. To put things into perspective, there are four roles that Teddy Sears is portaying in "The Flash," namely, Jay Garrick of Earth-1, Jay Garrick of Earth-2, Hunter Zolomon of Earth-1 and Hunter Zolomon of Earth-2.
This puts things about the man behind the iron mask into perspective. His face was covered by Zoom for a reason, and as fans will remember he had used a 5×5 tap-code to communicate with Barry (Grant Gustin) and Jessie (Violett Beane). Although when his message "Jay" had made no sense in "Escape from Earth-2," following the events of "King Shark," it is safe to assume that he is trying to tell them that he is Jay Garrick of their Earth.
It seems like the TV show is combining the back-story of Cobalt Blue and Zoom into one. As fans of the comic books will know, Cobalt Blue aka Malcolm Thawne, is the twin brother of Barry Allen who was raised by a foster family. He grew up bitter towards Barry for being lucky enough to grow up with their real parents.
In "The Flash" it looks like Hunter was the twin brother of Jay aka The Flash from Earth-2. In his desire for vengeance, he is looking to defeat the Jay's of both earths. He probably wants Barry's speed so he can go back in time and stop him infant self from being given up for adoption.