I just tried this and I think that in 40ish years of typing on computer keyboards, this is the most difficult thing I've ever typed. And I use emacs.
What do you mean? Super easy and fluid, I've been doing it for about a decade. Left pinky on left shift, left middle finger (you could try ring I suppose) on zz, tap twice.
I mean pretty much what I wrote. It's literally the most difficult thing I've ever typed on a keyboard.
Blame my hand geometry or the keyboard or muscle memory or 10,000 other things, I just noted it was super hard and unnatural for me to type that. (The downvoting on that is pretty epic, though.)
So weird, I literally never, ever typed :wq ever again after the first time I experienced the smooth bliss of ZZ. Maybe you're right about hand geometry and it's just for me. It's satisfying in the way that whacking ESC is, but smoother and gentler.