So you know how Zero Hour Parallax Hal Jordan kept popping up well after the Zero Hour event? Booster Gold ran into him traveling through time, Kyle accidentally attracted him to his time when he brought noob Hal home with him, and he was in that event where Tangent Superman fights Flash and other alternate universe meetups (Forget the events name, but am sure you know the one)
So.with it firmly established Zero Hour Parallax is out there, and has all his Zero Hour powers, what keeps him from discovering he loses Zero Hour, a new timeline then the one he remembers exists, and doing something different to "fix everything"?