If you are mowing for a lawn look or looking to cut your mowing time, i would go zrt. Seems you have tractors for doing tractor stuff.
You mentioned trees and ditches, but what about hills? Gates? All questions to influence which zrt? What is your budget? A better zrt that will last will cost more than a lowes or other box store residential. Easy to get up into big dollars quick.
I have an 2013 Exmark pioneer s series 60 inch cut with 27 hp kohler. You mention jd killin your back. I have comfort seat on my pioneer and its good. Better than others i drove when looking. Looking at total suspension seat for even better. Each brand usually has seat upgrade. I Went from 2.5 hour to 1 in mowing time. Have 3 plus acres that was field, so still little rough, with slight hill on back end with more area in future that i mow. I wanted more commercial like mower features with long term durability, great traction, power, big fabricated mowing deck, etc. as well as smoother ride. Also wanted local dealer i trust and a warranty i valued...so Exmark it is for me. Drove gravely, bad boys, and hustlers along with the exmark before deciding. The pioneer just felt the best to me for money paid. I suggest driving a demo of each you are looking at to feel the difference.
The makers you mention will all have there own models to meet your needs. What does your new holland carry for zrts? NH here carries bad boys and kubota mowers.
The folks on this site will be very helpful with opinions. They were to me. Each is serious about thier choice of mower they own and will tell the pros and cons of it.
Be sure, with zrts, that you compare apples to apples...each brand has residental level, almost commercial level, and commercial level mowers.