Ibrahimovic signed a one-year deal with the club earlier this month and is allegedly set to make his debut when the club travel to his homeland, Sweden, to play Galatasaray next week.
He has won 13 league titles in the last 15 seasons and will undoubtedly be relishing the opportunity to prove himself in the Premier League.
Speaking about his transfer, Mourinho insists he told Ibrahimovic to test himself in England.
“Let’s be honest, he’s very rich,” said Mourinho.
“He’s made money all his career, he’s won a lot of things, 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, China, stay in the French league one more season. So the guy wanted this one more challenge.
“When I told him that I had won in England, Spain and Italy and he hadn’t, that he’d done Spain, Italy and France, he thought: “Ahh, I want to go. I want to win every one.”
“So his motivation is high. His body is amazing. On Sunday he is going to start a specific programme we have prepared before he joins our group on the Thursday so he has five days just for him. So I expect he is going to be very good for us.”
Zlatan is one of the biggest names in football and expectations will definitely be high after he scored 51 goals in 50 appearances at Paris Saint-Germain last season.
He has not shown any signs of deterioration as he enters the latter stages of his career and the decision to retire from international football will allow him to perform at the highest level and keep up with the demands of football in England.
Mourinho has done an excellent job to complete the deals of Ibrahimovic, Eric Bailly and Henrikh Mkhitaryan early this summer and is still working on his fourth fundamental signing, who is believed to be Juventus midfielder Paul Pogba.