if barry changed everything to the point where even he didn't know what happened until it slowly came back to him, why did zoom know and practically planned his revenge almost from the beginning in order to meet barry again?
shareThough I don't know if this is made clear in the film or not, Zoom is a time traveling villain: He comes from the 25th century. Presumably his coming back should have changed time and therefore him as well, but he's remained constant. His own past experience with time travel probably gave him the leg up in understanding what it was that Barry caused, and given their near identical power sets it's probably safe to assume that if Barry knew the world as it used to be then so did Zoom (perhaps the Speed Force grants some form of immunity to temporal booms.) It's speculation to be sure, and not made clear in the film itself, but I think there are enough threads that can be connected for it to all make sense.
shareSpeedforce. Zoom followed Barry and had immunity to the effects because he's from a different timeline.
shareBasically Zoom lives outside time for lack of a better term. Because of his time travel he found he is unaffected by any time line change.
Ace Lions
What I actually had a problem with was this attempt for Barry to go back to stop his mom's death and have zero recollection he had done this. It only came to light at the end when Thawne told Barry. I know this was a focal point of the graphic novel, but there was absolutely no precursor to this until that scene. I mean, how did he even know that was himself and what he was about to attempt?
This was really the only flaw I had with the film--granted, it was the biggest considering it was the whole point of the alteration--but it felt tacked-on rather than being part of the narrative.