Cloud has the same calluses on his hands now that Zack had, white roughness on his palms and fingertips from the sheer weight of the buster-swords he favors. Zack traces them with the pads of his fingers, exploring their texture, and remembers.
He remembers snow, the year Cloud came to Midgar; snow there was as rare as flowers, but where the city-born were beside themselves either moaning at the cold or inconvenience or else romping in it like puppies, Cloud just put on an extra pair of socks and got on with life. It got so that, when the brief snowfall ended (leaving behind a sour slush), Zack was a bit startled to see Cloud's face out from under that curtain of silver-white. Snow and cold and the starkness of Shinra architecture seemed to suit him somehow; it must have felt like home to him, at least for a while.
Zack never knew if Cloud suffered from the heat in the summer months. Midgar was no tropical paradise - nowhere near as hot as Gongaga, anyway - but the metal of the Plate amplified the heat, and a mountain boy like Cloud couldn't have been comfortable. Still, in the short time Zack had known him, Cloud had never breathed a word of complaint.
He remembers the only time Cloud had shown discomfort, at least in front of him. Zack didn't blame him - crowded in like cattle in the back of a transport truck with no suspension to speak of along with the other members of his unit, a hyperactive Zack, and Sephiroth. The embarrassment would have been worse than any motion sickness, enough to send even Cloud Strife, stupidly stubborn to a point that impressed even Zack, into a fetal huddle.
Zack had meant to tell him some embarrassing stories about himself, but by the time Sephiroth was reliably out of earshot they'd had bigger problems, and then Zack was dying before he realized he'd waited too long.
But he remembers, with a soft glow of pride, how Cloud had trotted into Midgar, wearing Zack's clothes, carrying Zack's sword, filling the holes in his mind with Zack's memories, taking the strength he needed without Zack having to offer. And maybe he hadn't waited too long, then, because if Cloud could stand on his own two feet, even as broken as he was, then Zack was just fine with that.
The Planet, in the end, had a way of healing its own - they were both whole now, as much as they could be, and Cloud with his scars and rough patches is glistening like soft gold and chocobo down in Zack's arms. Zack twines his fingers in with Cloud's, and smiles, and remembers.