I just read the Busiek/Perez Avengers story with Nefaria in it (good read), and he seemed just as powerful in that story as he did in his first run ins with them. Can Zoom speed steal like the Flash?
Well I can't recall an actual fight between the two that wasn't just an altercation or something, but I do know that he was able to do battle with an amped Wally. At the time, they were fighting so fast that superman looked like he was a statue suspended in air. He had no idea what was even going on; they were so fast that they didn't even register to him even with his level of speed and reaction time. That's how fast zoom is, and when wally started losing his amp, zoom started taking him apart. Keep in mind, this was zooms normal "speed", and wally had to amp intensely just to keep pace with him in an actual battle.
It's been explained that whenever zoom fights or is defeated, he does so to make his opponents "Better heroes", which implies that when he loses, he may be doing so just to teach a lesson, as opposed to his opponent being outright superior. This is not to say that he cannot be beaten, it's just a way for DC to explain why most top-tiers can even see him, much less beat him lol.