How did Zoom do it? Story premise is wack.

It's implied through the film that Zoom was responsible for the new timeline.

But at the end, we see Flash going back to stop his earlier self from saving his mother, and thus resetting the timeline. So Barry did it, and Barry undid it.

So, how was Zoom involved at all? He's from the 25th Century, but in the new timeline, the world ended about now. How is Zoom in this timeline, and aware of the original one?

Unless he was sneaking along next behind Flash when he made the change. Which is impossible since the story hinges on the "Speedforce" not being strong enough to allow two Flashes to travel in time.

Or does Zoom have another way to travel in time?

Also the whole explanation of how one tiny change in history -- one woman survives a home invasion -- causes Armageddon is absurd. People travel in time constantly in the DC universe, they never have such drastic "butterfly" effects. They even acknowledge that many of the changes preceded Barry's mother's death, but just handwave it away.

While I liked Aquaman and Wonder Woman destroying the world in a lovers' tiff, the basic premise of the story is nonsense.