If you look on the picture of the gang (in serapy's post) then you see another "figure" behind Cid. All this points to one conclusion, Zack was cloned before he died and whilst one became a soldier the other opened up his own flower store and ended up travelling the world. He eventually died at that point and any photo that gets taken there, he's in.

Oh my god guys, its like...the ring, where it shows their face distorted whenever they've rung the phone and I'm seeing comparisons between the other ghost Zack and the girl from the ring here, they're in cahoots! Look at A) The link between games and films, they're both media so they're bound to be connected and B) The way I type this confusingly which confuses you, you'll see the light.

I should become the new wacko who posts theories about ff7 instead of ff8.