The following post is a theory on how Jay Garrick became Zoom through Velocity 9.
When Zoom was revealed at the end of The Flash's King Shark Episode (The Flash season 2 Episode 15) to be Jay Garrick or what seems to be Jay Garrick played by the same actor Teddy Sears, fans were shocked, but also disappointed to be left on a cliffhanger. While the fans theorized how Zoom could possibly have been Jay Garrick these past weeks the show was on break, I was able to make my own theory (With the help from other The Flash fans) on how Velocity 9 ended up created Zoom through Jay Garrick. Now any fan theory is just a theory without confirmation, but I do believe that when Jay Garrick took the Velocity drug, it created Zoom, a second persona if you will, and I can tell you why.
When tonights episode was released at the time I am writing this post, March 22nd's episode of The Flash (Season 2 Episode 16) featuring Trajectory, a lot of hints and reference were dropped not only related to the Flash comic, but also about Zoom's origin. Quick of the summary of the episode would be that the show introduced a new speedster, Trajectory, who gained her speed abilities through reverse engineering Caitlyn Snow's formula Velocity 9, the same formula that was given to Jay. It was made her fast, faster than Barry ever was, same as Zoom.
When the scene with Eliza (Trajectory) was showed with her by herself having internal conflict wether she should continue using the drug or not, her conflicted side was shown as a second persona, Eliza, in the Trajectory suit. The drug assuringly split her mind into two persona mentally, created a "bad" version of herself as the speedster Trajectory opposed to what seemed to be, quoted from Caitlyn to be a good person.
What if when Jay took the drug back on Earth 2, since it was revealed that Jay had taken the drug before, did the same thing to himself. Created a second persona, an opposite to the Crimson Comet, a hero who would help people, to Zoom, a villain who would terrorize people. This would explain why we only see Jay fight Zoom through his words. Also, it is shown that Barry is faster than Jay was when he was The Flash, yet Barry could barely keep up with Zoom, while Jay, in the fight shown, showed Jay almost on par with Zoom's speed. This would maybe tell us that the reason that's the case is because Jay, this whole time had been fighting Zoom in his head, never really being able to catch him, but close enough to see all the things Zoom has been doing, meaning they are the same person.
Though I do not believe Jay, our Jay, is truly evil, because unlike Eliza, I don't think Jay was aware of his dual personality, since the show has shown him to be such a good hearted person, unless he's a very good actor like someone last season (Thawne). Also, people may debunk this theory claiming that Jay can't be Zoom, since Zoom was holding Jay's lifeless body and the end of episode 15, contradicting this whole article since they were both at the same place at the same time, but I can explain that too. Jay said the drug he took had a lot of unexplained negative effects, one being cellular degeneration. What if another one of the effects was causing the dual personality to materialize, becoming it's own person through the speed force. While Eliza got split from Velocity 9 mentally, Jay most likely got split physically, through, unlikely, but possibly, mitosis.
With all these hints and facts, this show is dropping, I do strongly believe Jay created Zoom through Velocity 9, this would explain why they gave us a red herring that Jay's doppelgänger is Hunter Zoloman, Zoom from the comic. This way, the creator can have Zoom be the same as his comic counterpart (kinda), and be something original at the same time. I do acknowledge however that this theory still leaves a lot of unanswered questions like, why would they actually kill off Jay Garrick if he was the real Jay Garrick, or who is the man in the metal mask, and is he the real Jay Garrick or at least a version of Jay Garrick, but the theory I came up with seems to be the most plausible, in my opinion, on Zoom's origin with how the show is dropping hints. Again, I could be wrong, but we won't know until the show finally give us a full explanation in future episodes.
Thank you for reading my first post/article relating the topic of The Flash. It was a true experience and I do encourage anyone to feel free to give me feedback on this article and add-on in the comment to why, or why not you believe Zoom is Jay's dual personality.