User blog comment:SuperBen 1000000/Damien Dhark vs Zoom/@comment-28419685-20160509165003/@comment-28419685-20160510114502

Zoom's superior recon tactics allowed him to deduce Barry Allen's carefully guarded secret identity as the Flash of Earth-1, well before their first face-to-face meeting (as "Jay Garrick" still in the beginning of Season 2). Now imagine him applying those recon tactics against Darhk, whose family was easily discovered by small-time villain Lonnie Machin, followed by Team Arrow - and that was before his wife decided to literally run for mayor of Star City. With all that in mind, I'd say it's a 99.999% certainty that Zoom discovers Darhk's family AND his source of power.

Speaking of his source of power, does Damien's immortality persist without it? To me, the show has clearly indicated that it does not - we already saw how weak he was when Team Arrow deprived him of it. Fortunately for him in that case, he was defeated by heroes who simply threw him in jail out of a sense of mercy and restraint. But imagine how that would have played out if it was Zoom in the shoes of said heroes...