“Let’s be honest, Zlatan’s very rich,” he said. “He has made money all his career, he has won a lot of things and you only come to the most difficult championship in the world if you feel you can do it.
“If you don’t feel you can do it you go to America or China or stay in the French League one more season. So the guy wanted this one more challenge.
“When I told him that I had won [the championship] in England, Spain and Italy and he hadn’t – that he’d only done it in Spain, Italy and France – he thought, ‘Ah, I want to go. I want to win every one.'”
Mourinho is still chasing the final piece in his United puzzle in Paul Pogba.
At his unveiling Mourinho said he wanted four new players and so far has signed Ibrahimovic, Bailly and Henrikh Mkhitaryan.
A move for Pogba would break the world transfer record and could see United installed as title favourites.