What's interesting tho is Zoom mentions that like in the comics, Earth-1, Barry's Earth, is the lynchpin to the others, which suggests that it would be easier to travel from one to the other from there.
Most likely the more advanced technology of Earth-2 would make the research of the trip easier.
Also, I think we can all agree that since the show's Earth-2 is not that similar to the one(s) from the comics, their Earth-3 is not similar either. Cause in the comics, all the heroes are villains, which would mean Jay is likely an even bigger Baddie that Zoom.
I'm holding out hope (and so is Shipp, based on his interviews) that Jay's Earth is the same one that the surprise character came from at the end of Legends of Tomorrow.