Why does Cloud have the memories of Zack? That's a point I still don't understand :(

When Zack and Cloud were being experimented on by Hojo in the Shinra Mansion Basement, their thoughts merged. Therefore, cloud has Zack's memories. When Zack was killed by Shinra Soldiers on the way to Midgar, Cloud took Zack's sword (The buster sword) and became a Mercenary.

thats interesting!:cool:

Well more obviously, Cloud and Zack were both in soldier together. They went to the mako reactor at Nibelheim with Sephiroth.
They were both friends.
Cloud's delusional world, where he calls himself a soldier first class is essentialy him trying to be like his best friend Zack!

Play the game through again and pay more attention to the FMV's. It will become much clearer.