MY solution to this would be to rotate the strikers equally, plain and simple. How would Zlatan learn if he doesn't have any reference to learn from right?
He could learn a few dimensions from Mutu, Trez, and Alex's game. Come to think of it, I only realized now that all our strikers have different kinds of playing styles. Which is good of course.
As I said before, from experience, whenever I got injured and had to watch from the recovery table, I always came back with some new dimension in my game. Something I picked up watching my teammates play. I only played in high school and college ball, but you figure out the logic.
Giving yourself some time to watch, also gives you a chance to LEARN.