After rewatching the latest Flash episode I've realised that the suit Iron Mask is wearing is very similar to that of a flight suit, and hes using tap code to communicate which in real life was used by soldiers in the Vietnam war. I've come to suspect that Iron Mask is actually Hal Jordan / Green Lantern, who is a pilot. It's been hinted towards for a long time, a pilot named "Jordan" making a brief cameo in the Arrow episode "Green Arrow" in the flashbacks, and now with Supergirl being connected to the Arrowverse via another Earth, that means there is aliens in the Arrowverse, which means Supergirl probably has an Earth-1 version somewhere so why not an Earth-2 Green Lantern. When Barry asked about Iron Mask Zoom said "you wouldn't believe me if I told you", but he might mean something like they won't believe if he explained what Green Lantern is and what he can do. Why Zoom has Green Lantern locked up and alive, and how he does, I have no idea but it would be so f***ing epic if it is him.