That's nuts, I'd be scare of stability at any real speeds.
My zero turn will move pretty fast, has a 27hp kawasaki engine, but I bet it doesn't really do more than about 15mph at max speed without the blades engaged.
Lawn mower racing is a sport out here in Hicksville but the blades are removed, they don't reach those kinds of speeds on an oval track, and alcohol is often involved. I'll bet money that the blades on that don't turn fast enough to mow at 100 mph!
I've got the Kawasaki 23 hp on my zero turn and I can mow at 8 mph.