User blog comment:Gracchus Mccarthe/If you don't yet know it, I'm obsessed with all things Zoom. I believe my first theory about him is correct. This post shows why./@comment-27779929-20160327144208

Jay is from earth-2 and Zoom (Hunter Zolomon) is from earth-1, using V-9. He got trapped in a breach and traveled to earth-2, going some time back in the past there and became the arch enemy of Jay, not able to return to earth-1. After all the breaches opened again, he was able to travel back as Hunter Zolomon to keep an eye on Barry and Jay..