Continuity mistake: Batman is blasted against a green car by the guy with heat vision. He runs to the next vehicle as the heat vision guy shoots a ray at the green car, and the next shot shows the car is now purple. (01:01:40)
Continuity mistake: When The Flash is on Batman's computer, the number of windows cracked/smashed changes between shots. (00:45:10)
Continuity mistake: Lois hides under a purple car. It becomes red after a beast walks over the bridge. (00:39:15 - 00:39:45)
Continuity mistake: The Flash is back at Wayne Manor with Batman, after regaining his powers. In the wide shot of the Manor's interior, the windows are about 5 feet in height. The next shot shows the windows now only about two and a half feet in height. (00:45:05)
Continuity mistake: The Flash trips in a field with loads of cacti. One of them changes in appearance between shots. There is also a two foot tall cactus with no branches next to it that disappears. (00:43:10)
Answer: Flash couldn't travel through time later in the movie not because Zoom was alive but because Zoom was also tapping into the Speed Force, preventing Flash from gathering enough of the Speed Force to break the Time Barrier. When Flash originally went back in time it's likely because Zoom was in custody, therefore not tapping into the Speed Force at that time.