Some of the box store ZT's like my Craftsman 6000 don t do hills at all. Even with bar lug tires, it wont hold on very much of a side slope. My Ferris IS700 will take the steepest hills I have and hold a straight line across a 20 degree slope with ease as long as the grass is not wet. It handles slopes as well as my JD 332 tractor type mower would.
It seems ZTR slope handling all depends on the weight of the mower and size of the tires, the heavier the mower and larger the tires, the better it handles slopes. Going straight up and down a slope, I have no problems with climbing a 40+ degree slope with either mower. I have never had either of my mowers try to tip backwards when mowing up a slope. One of my ponds has a very steep slope on the dam that is hard to walk up but the mowers climb it well.
