Mirotic is going to be a hard player for the Bulls to trade.
First off, Niko has a NTC this season, so he has to approve any potential trade. Secondly, he has a huge salary that will be hard for another team to match without sending back a crap contract.
But I can understand why the Bulls want to trade Mirotic, and Lopez also. These guys are adding wins to a team that is trying to get a top lottery chance. And with Niko playing as well as he has since he returned from his broken face (and pride), now is the best time to try to fool some other team into thinking he isn't the same inconsistent player he has always been.
Robin Lopez would be a great acquisition for many teams, though. I'm interested to see what they can get for him if they really do trade him.