He has scored 26 goals this season and is showing no signs of slowing down despite his advancing years.
Amid speculation he is holding out for a two-year contract extension at United, Ibrahimovic spoke warmly of the club and Mourinho's influence on his performances.
The Swedish striker arrived at Old Trafford on a free transfer from PSG last summer and many questioned whether he would be able to cut it in the Premier League in the latter stages of his career.
While Manchester United are mulling over the contract, Zlatan's agent Mino Raiola is in talks with Major League Soccer (MLS) side LA Galaxy.
Speaking to BBC Sport, Mourinho said: "Zlatan is not a surprise for me".
"Because of the professionalism, the training and his commitment to the club".
"It's not personal what I have". A lot of United's success has revolved around him.
"First he called me every day to have me and from one day to the next I didn't play anymore", he said.
"There has to be a dip at some point". And a player of Zlatan's status wouldn't want to miss out on big matches, and under the circumstances, Jose Mourinho will have a tough time to hold on to the Swede global.
Ibrahimovic is, however, available to play against Rostov in the Europa League on Thursday.
He missed the 1-0 defeat by Chelsea in the FA Cup on Monday, and will be absent for United's next two Premier League games against Middlesbrough and West Brom.
"The bad is that at times maybe his form hasn't been as good as it was last season".
"There's potentially always going to be a fall in a young player". He can have confidence knowing he will play.
Yogi Adtiyanath sworn in as Uttar Pradesh chief minister
He is also a member of 16th Lok Sabha, representing Ghazipur Lok sabha constituency and was also elected in 1996 and 1999. BJP has made Keshav Prasad Maurya, an MBC, a deputy CM, while Yogi Adityanath, a Thakur, has been made CM, she added.