Ctrl+ and Ctrl- work very well for me, in all my computing environments. I’m very accustomed to using those, in part because they’re supported so widely, and especially in browsers. Scroll wheels have a variety of functions in different apps, so I don’t “expect” to zoom that way (although it’s fine in most contexts, some graphics apps do very different things with it). So I cast my vote for the Ctrl features.
That said, I wouldn’t mind at all if most of these display and format settings were document-specific, but I’ll leave that for Darren to evaluate. I write a lot of different kinds of material, and it is definitely helpful to have visual distinctions among them, including size, fonts, page background, para styles, etc.
But I’m trying to keep my suggestions within the scope of primary functionality while the program is still so fresh and simple.