I think sherloque is saying clever girl because he stumbled upon something the others don't know, it has to do with the symbols barry was writing when he first came back from the speedforce, which is exactly the same as whats in nora's book. He's putting pieces to a puzzle together but hasn't told the others yet, probably becaues its all speculation until he finds out more to prove his point.
As for zoom, theoretically he should've been able to catch nora no problem, reason being the zoom at that moment in the time line was already ridiculously fast, he then just stole barry's speed making him even faster...However the version of barry with nora that showed up would smoke zoom easily now. After barry lost his speed but then regained it, I believe he also gained more speed or somehow developed the will to go faster because he was just as fast as zoom when they raced, they were pretty much neck and neck so barry at that point was already on par with zoom. Savitar is faster than zoom, and current barry after being in the speedforce and soaking up some of its energy is even faster than savitar, even wally commented saying he had never seen any speedster go that fast, that would include both zoom and savitar...plus what other speedster has phased and busted through one of star labs prisons for meta's the way barry did when joe kept telling him "iris is gonna die"....anyways I think the reason the timeline wasn't affected was because when zoom was grabbed by the wraith they were traveling in the speedforce or as i like to the call it the tunnel of time, so that's maybe why it never changed the whole savitar scenario, ect.
btw barry probably protected nora so zoom wouldn't catch her by blocking him and keeping infront of him so nora was out of the way, don't matter they got away anyways.
