May be missing something here, but ...
A nonseparating zip just means that you can't completely separate one side from the other, as with a jacket, as pointed out above. The zipper still does separate at one end and all the way to the point where connected at the other end.
But since the top of the zip, at the tent apex on your pic, is always joined, you don't need the two sides of the zip to totally separate. You zip down from the apex, where the zippeer is always joined for and inch or less, to close the fly or canopy entry, and back up to open it.
Or maybe I am still missing something.
If you use a nonseparating zip, cut to desired length, you have to know how to mount the slide(s) on the teeth. This is a little tricky at first, but doable once you get the idea. Instructions are not hard to find-check out Quest and OWF. I use the chicken-heart method - sew the zipper in place with the slide mounted, moving the slide out of the way of the presser foot when the work reaches it on the machine.
Have tried making zipper stops from blobs of epoxy glue, and got it to work fine. But even epoxy can release its grip, so the foldback and sew approach described by Nicholas is the most foolproof.
Don't mind being told if I am way off base here.
P.S. Please sew, or weld or whatever, some zips on cheap material before you begin working with that cuben. Unless you are a Wall Street broker, of course - then it won't matter.