Other mistake: The television news report about the battle between Captain Boomerang and Citizen Cold has a message scrolling across the bottom. The problem is that the words are moving from left to right, which forces the viewer to read the message backwards. (00:12:40)
Other mistake: Cyborg confronts Batman about throwing Yo-Yo off the roof and then turns on a hologram projector in his arm to show other super heroes. There is a beam emitted from his arm generating the holographic images. We then see him turn the beam off, yet the holograms remain and they have a conversation with them. (00:17:55)
Other mistake: In the flashback of Bruce Wayne getting killed, his mother is cradling his body and weeping. She has his blood all over her hand from touching his wound. She rakes her fingers across his shoulder and down his chest with her bloody fingers, leaving no trail of blood, but when she places that same bloody hand on her face it leaves blood all over her face and mouth. (00:35:05)
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.