-snip- It was a very smart move taken by AC Milan's management. -snip-
It is too early to conclude a smart move or not about signing a contract with Zlatan. He just played a few matches and seemed not really presenting big influences to the team. Let's see till the end of the season to conclude it. 
-snip- They took Ibra to raise the morale of other players -snip-
Agree. One of the purpose is to make the morale of Milan's team be stronger and have a winner mentality in each match. We can see from the last few matches that Milan can be the winner and the team looked more solid and confident. Your first and second reply seems a bit contradicting to each other. You said Zlatan is not really giving big influences in the last few matches but on the second reply you say that Milan can win some matches after Zlatan in and Milan looks more solid and confident.
At least there is signficant influence for Milan since Zlatan came to the team. Proven by their last several matches without a lose while they got worst results before Zlatan was in the team.