I've been using a Zephyr for several years (it's the first of my panoply of TB bags). It is certainly a well-padded bag, and the sides, are padded and stiff as well.
I can't be completely sure, since I no longer have my Hasselblad 500C and my Mamiya 645 cameras, but I'm thinking it would be a pretty tight fit. The Hassy might have just barely fit, but I can't see the Mamiya going in well, particularly with a lens attached. And, you don't specify what else you would need to carry in the way of photographic accouterments.
I'm afraid I can't think of a TB recommendation. The larger shoulder bags (I own a Super Ego) are not sufficiently protective and rigid for "bare" camera equipment, in my opinion. I would still go with a traditional, compartmentalized photographic bag. By the way, the TB Camera Insert would not hold the equipment mentioned above.
Hopefully someone else will chime in... but, as you might expect, most people will say, "What's a medium format camera... a special camera to photograph spirits?" (I teach an intermediate photography course, and 3/4 of the class has never used film!)
Wish I had more definitive guidance for you.
Someone please help me!
I have BAS (Bihn Acquisition Syndrome)!!