The 25 year old arrived at Eastlands in January in a £27million move from Wolfsburg after building a formidable reputation in Germany.
The Bosnia striker scored a remarkable 66 goals in 111 Bundesliga games and earned a lucrative four-and-a-half-year deal with City in the process.
Dzeko has found the target four times in England, twice against Notts County in the FA Cup - City needed a replay - and twice against Aris Salonika in the Europa League.
Mancini said: "It is difficult for him, it is difficult for me, but it can happen when you change teams. It is important he works hard, only this.
"I believe Edin is one of the top strikers in Europe but sometimes incredible things happen to strikers. You can score, you don't know why.
"On the other hand, (Wayne) Rooney did not score for months, the same for Torres. This is an incredible situation for a striker. But I am sure next season Edin will be fantastic for City.
"Now we have six games and the FA Cup final and Dzeko can score important goals in this time."