He has done brilliantly but he has also been responsible for quite a few cockups which mainly seems to be down to his lack of appreciation of defending.
It's not impossible he could learn it, but he also lacks pace & defensive technique, even yesterday, was left easily on about 3 or 4 occasions, which Otamendi etc cleaned up.
His football skills are now coming through & rather than just knocking the ball around, he's creating stuff which is probably at a higher intelligence level than Mendy can produce, but Mendy (when fit) has that pace & power to go with a vicious cross.
I hope we don't replace him with Ben Chillwell as the only advantage I can see there is that he's bigger. He's nowhere near as good a footballer as Zinchenko & not a great defender.
But if Pep is going to sign 3 players, one of whom is a fullback, I don't see how that's possible with Zinchenko staying. We won't have squad space.