I mow very steep slopes with a zero turn mower. If you are confident and smart about it, you can do just as much as the Cub Cadet steering zero turn or a 4WD Scut, and be faster. You just need to understand a couple of key points - the zero turn will go uphill very well, but has poor control coming down, and has a limit to sidehilling because of course the casters can't be held straight ahead. I'm no fan of Cub Cadet because although some of what they have built is quality, a lot is poor quality. Cub Cadet has poor resale because of this, and their primary reputation is for making cheap riding lawn mowers sold at the bog box stores. That said, the steering Cub looks to be good quality although it is still not quite as fast as a traditional zero turn because you can't turn the wheel as fast as you can operate lap bars.
With a zero turn, mow on diagonals. Mow up, and back down. Or, turn around and go down at a diagonal. The mower won't hold as well on the way down, but it might be adequate. Mow a chevron pattern in other words. It is possible for the front end of a zero turn to pop up while heading steeply uphill. Be prepared to immediately yank the bars back towards you. If a side rollover is imminent, turn immediately downhill. Never mow with a zero turn above anything with a dropoff at the bottom or water. It isn't worth the risk.
I ran a Simplicity Legacy "yard tractor" for a few years. Great machine, way better than most riding mowers. It had big tires, rear diff lock, 25HP Kohler Command, 5 gallon fuel tank, 60" belly mower with hydraulic deck lift and electric cut height adjust, power steering, etc. These Legacy mowers could actually be had with a Cat 0/1 3-point hitch and a small loader, and we also offered with a small diesel. They stopped making them just a few years ago. Otherwise, I think the JD X700 series is probably the best machine in that class, as they can be had in 4x4, 4-wheel steering, various engine choices, etc.
If I was buying a SCUT for lawn mowing, hands down the Kubota BX series tractors. These are high quality machines with great engines and some nice features. These are the best-selling SCUT on the market, and resale value is high. If you want to compare Kioti (the Korean clone of a Kubota), they are nice enough but I always make the comparison of Toyota vs Hyundai.