Zhang flattens him early, Carnera has no defence against the offence of Zhang, which is quite versatile, you have to worry about both hands, and on top of that, he sets up punches well, he jabs the the body, he throws a light lead hook to set up the back hand and he sets up the power lead hook well after throwing the left to the body, Carnera is also stiff which would be terrible against Zhang’s offence. Zhang would go straight at Carnera, lead straight lefts stiffening Carnera down the middle, tapping to the head and stabbing that left to the body, lead hooks to set up the straight left down the middle, he’d also dominate him up close, he’s much faster and shortens up his punches better. Carnera would be there for all of it, the straights because he’s stiff, and they’d land too often also because his feet were cement like, he’d have no deference for what Zhang has, he’d freeze on the inside also, want to get back on the outside to get a break, but he wouldn’t get one, he’d just get broken instead. This is Zhang vs Joyce 2 all over again.
In Carnera's defense, he was much more mobile and quick than Joyce while also possessing a formidable gas tank himself. with the right (dirty) ref I'd like to see how Zhang's gas tank copes in the clinch against a very strong and formidable clincher like Carnera from the Loughran fight. Only problem is that Primo likes fighting from range and trying (emphasis on trying) to be slick defensively a little too much....
I don't think that Carnera ever fought a southpaw, certainly not a southpaw his own size. I don't think that he would have an answer for Zhang's left hand and that might not even be his biggest problem. Because Zhang beat Wilder and his right hand with his own right hook. There is a possibility that, if Carnera keeps getting up and the fight isn't stopped, that Zhang will tire out and Carnera could make a comeback but I wouldn't count on that.
I am going with the more proven Carnera, but Zhang would be very dangerous for him . I actually think that Zhang could have been something special if he had got into the professional game at a younger age.