Just a couple slight incline/declines in the front and around the septic mound. Only one big tree to go around. I’m looking at a few used mowers in my area (Pennsylvania).
• "Zero Turn" mowers typically don't like to traverse inclines, especially around lakes and other dangers. You'd need to limit your travel to strictly up and down paths. This because ZT's can/will loose traction on the 2 wheels that matter and start to slide. But they can really make a difference if you have a flat-ish yard with lot of trees to go around.
• So you're proabably looking for a 30/32 inch "garden tractor" style mower. Most of these are built by MTD and simply
rebranded as J Deere, Ariens, Husqvarna, Craftsman, and 30 others. (You'll see the similarity when you look for it.) These are fairly reliable, but to me the main drawback is cutting heights. From the driver's seat it may look like there are 6+ cutting heights, but if you get down and measure there's typically only 3 to 4 useable. If you have a specialty lawn and really care about the mowing height, then keep looking. Otherwise, rate by seat comfort and price.
• Look for something with a name brand engine: Kawasaki, Honda, B&S, Kohler, etc. Chinese engines are common and I would steer you away from those based on parts availability in 4 years.
• I would also suggest you steer clear of "electric mowers" of any brand. There are always battery problems of some description that turn up in 18 months.
