Sorry, maybe this was addressed (I skipped a few messages), but I wanted to share something.
@Fiz, I once thought the same thing you raised earlier, that the defeat of the Whispers rewrote parts of the past, specifically in regards to Zack's death and Stamp's design. Then the Ultimania released. @aitaikimochi, FFVIIR's translation queen, tweeted this passage and it convinced me otherwise.
"What doesn't make sense about this is how is it possible that there are two different Clouds that exist at the same time?"
I find it
really interesting that the Ultimania doesn't consider the Zack holding an unconscious Cloud to be a flashback. It specifically asks how is it possible that these two Clouds (plural) do not see each other. The only way they can exist at the same time and space, yet somehow not the same time and space, is if they exist in separate, slightly offset timelines. That's my thinking anyway.
This would also match with what we're shown visually. Earlier, at the end of the Midgar highway, we're shown Zack confronting the Shinra army at the same time the party confronts Sephiroth. With separate, slightly offset timelines, this would mean these two scenes are actually happening congruently.
How the Ultimania presented this question is what changed my thinking. Just thought I'd throw that out there!
I also want to point out that the Ultimania
specifically points out that Zack lives past his last stand as it was written in the original game. I hope this puts to rest any theories that Zack will get shot by three lone grunts a few steps later. I, uhhh, really don't think that's the direction they're going with this...