I have a midsize ZTR. Just run it up the trailer ramp with one side hanging off. I use an impact wrench to get the off. Some guys just use a wrench. That part is personal preference. But if they've been put on with an impact, it will take one to get them off. Most unscrew like a regular bolt. Counter - clockwise to unscrew. Also, make sure you troque the blades properly when putting them back on.
Where can you get a jungle jack? I saw a Craftsman commercial and they were using a jack on a riding tractor to get under the deck. I think it was the Motorcycle/ATV jack. I think it would fit under a ZTR, I was thinking of buying it. I think I saw the price at $100.
Just in case you are not then pull the mower back to the edge of your trailer. Push down on the handle bars, attach a bungie (rubber) strap hook to the ramp and other to mower. It will be up about 3 feet. Now when you need to put gas in it unscrew the cap.
For large WB and mid mounts we use a sizor jack from a junk yard. It is a compact type for lifting a small car. When it is lowered it will go under a deck 2 inches off the ground. And here's the best part, it has a 3/4 nut to turn with the tire tool for heigth, but at the shop we use an impact on it. Raises the machine very easly and the impact is already there for the blades, a simple swap of blades take less than 2 minutes.