Zoom is confirmed to be the main antagonist in season 2 of The Flash. But so far the identity of Zoom has been left ambiguous...or has it? I believe we have already been given clues and hints to who, or more accurately, what he is. Let's begin.
In 2x02, Jay Garrick describes Zoom as:
"He is an unstoppable demon, with a face of death."
Jay Garrick may have been more literal than some of us may of thought. I am obviously talking about Zoom being the BLACK FLASH.
As the dialogue correctly states, the Black Flash is the Grim Reaper to speedsters. We know that Zoom was obsessed with killing Jay Garrick and now he is obsessed with killing Barry Allen. So that fits.
The executive producer of the show, Gabrielle Stanton, described Zoom as:
"He is a mega, mega villain in the Flash canon."
So Zoom is a comic book villain and not a creation of the show. My theory fits again.
2.) Visual Appearance
To me that looks more like a skull than a human face in the picture above. Still not convinced? OK, then look at the Flash vs Zoom fight animatic.
You've got to admit, that looks a lot like the Black Flash.