Trektop NX, but this is the sequence I've landed on after 5 years.
1. Open sunrider. This seems to relieve some of the tension on things and make stuff easier to bring together.
2. Stick the rear end of the top edge of the side window under the velcro flap on the top to hold it up while I start the zipper about 4". Repeat for other window, and then start rear window zippers by about 4".
3. Put front edge of side windows into door surround channel.
4. Zip up side windows
5. Put bottom edge of window into tub channel starting at front and stopping before the tub curves around to the rear.
5. Zip both sides of rear window and secure in tub channel brackets.
6. Finish putting side windows in the tub channel around the corner and then in the brackets overlapping the rear window.
7. Secure all velcro, flip sunrider closed and secure top in door surround channels.