That's what I'm doing but I complained in a feedback to Apple. It may not have been standard UI before, but it was that way forever so imo it wasn't broken and they fixed it anyway. Bad! Now it's inconsistent because you have to option-click the zoom button to get to the mini but you can just click the zoom button on the mini to get the big window back.
I guess they painted themselves into a corner. They should forget about using the zoom button for this function. move the <-- || --> buttons over a hair and stick a whole new colored button on there for mini-max function. Leave the zoom to be zoom the way all other windows react to zoom (which so far only a few posters have said they actually use in iTunes anyway).