The basic outline of where to split the company seems straightforward to me.

AWS get split off first and foremost, that part is blatantly clear to me.
From there, the retail webstore (what we generally think of as “Amazon”) gets split off from its broad category of services: music and movie streaming and everything in that category.
After that, split anything that involves designing/repurposing other designs and selling a specific consumer product off. Kindle, Alexa, Roomba (if that purchase goes through), Amazon Basics, etc.

I think there’s a decent amount of room to get more granular with the process, but I think that covers it as a basic outline.