Hi, im a newbie here but i think i understand the game and film pretty well, and after watching the film i played the game again, paying particular attention to the details (i.e. if there was anyone ever name kadaj in niebhliem)
Anyway to put the original post to shame, the sick guy who is in the tube is NOT ZACK. First off dont you think that Aeris would recognise her old boyfriend?? (being the caring gentle creature that she is) then this sick guy has a tatoo on his arm (i think its 2 or something)
But first ill scientifically prove that the man in the tube is not Zack. How? Well if you dont understand this then you need to play the game over and over and see the secret flashbacks and cut scenes.
After sephiroth burns down neibhliem *sorry about spelling* all the surviors are grouped up and experiemented on (men in black capes - sephiroth clones) both cloud and zack are in this group, however they escape.
But when reading the journals in the shinra mansion you can see there are two speciemens, one that accept the jenova cells (Cloud) and one that rejects them (Zack)
Now, heres the science! Jenova cells contain jenovas thoughts, and people who have jenova cells are controled by Jenova. (including sephiroth & cloud), now Zack never accepted the cells so therefore he wouldnt obey Jenova.
Where is this going you ask? The sick man is a sephiroth clone (i.e. his tatoo) and has been infected with Jenova cells. And if you go back to him in the tube after the "Sephiroth Reunion" he has gone, ask the person beside the tube and he tells you that he has walked away mumbling "reunion". This couldnt be Zack, he would have never heard Jenova/Sephiroths voice as cloud does during the game.
There!! And finally! Zack DIED before you started playing the game!!!! So you cannot possibly say that he is in the game because hes is not. So the orignal post is just BS. Ignore it. Besides its way to vague to even follow.
There.