How would you break apple up?
And why?
I'm no regulator, don't ask me how to do it! I just think it should be done.
I'm not too certain how anti-competitive Apple is. If it's anything like Microsoft it should have some things that could be broken up, like bundling software together with hardware and OS. What Microsoft do to plug their browser and the Bing search engine on Windows PCs is anti-competitive in my opinion. If Apple does anything similar, which I assume it probably does, that answers your why question about why I want to see it done.
Of course Amazon, Facebook and Google are the worst when it comes to being monopolistic, so they should take priority ahead of Apple and Microsoft for regulation