I think the comp of Alcaraz and Nadal is a bit lazy, probably due to both being Spanish. Someone called him a chameleon, and to me that seems more apt. A bit of Novak, a bit of Rafa, a bit of Roger...and really, his own combination. But he also has his own weakness, which is hard to pinpoint...perhaps part of his chameleon nature is switching into a kind of lost little boy mode.
One thing about Zverev: his movement is underrated. He's getting to balls in a Novak-esque fashion. I think he looks slower than he is because he's so big and lanky. But he seems to lack any magic to his game. He is ferocious when in a groove and just hammers the ball, but he doesn't quite have that x-factor that the greats can pull out.