Zibra is an incredibly gifted footballer, but he does lack application. While work rate isn't everything, in England it does count for far more than in most places, and as such I don't think he'd be suited for the Premier League.
Also, he though he is undeniably strong, he can be bullied by tough central defenders (see Champions League semi-final).
But, none of this matters are City aren't interested in him and he has said the English climate means he doesn't want to play in England. On a note about Tevez, I've always felt that his work rate covers for certain other short comings (lack of pace being key amongst them). That being said, the last thing Madrid need are more forwards, and if Mourinho does decide to look for a busy Argentine forward coming off a brilliant season, early rumours in Madrid already have that forward as being Diego Milito.
I'm not convinced Tevez is particularly happy at City, with Mancini, etc, but to his credit he is a professional and I think he will work hard as long as he's with us. I doubt he's a blue for life though.