I guess I am fortunate, or just very patient. I simply bought a glover's needle and some outdoor heavy nylon thread at the local fabric store and hand stitched my surplus door's window zippers back in by hand using the original holes. Just go one hole at a time. Once you get in the habit, and into a rhythm, it moves along well enough.
It takes about 35-45m per window, but luckily I only had two to do. Front doors of course, the harder ones to get new for a low price.
I thought of using my Speedy-Stitch, I have two, but it is more aggressive in terms of needle size as someone already observed. This made me worry that I'd get off track and end up with a badly wrinkled zipper. I resigned myself to hand stitching through the old original holes, but then it wasn't as tedious/hard as I thought it would be once I got going. Every few stitches I backtracked a stitch to double up the thread. It's holding fine 8 months now.
I certainly would have liked to be able to use a machine, but it's usually just me and that is a two person job to wrangle those doors around. I have a friend who retired from the custom cycle business years ago. He has an old professional long-reach sewing machine for doing bike seats. When he moves to his retirement home in SC (from MD), I am going to try to talk him out of moving that machine. (And out of several other items from his ample warehouse of antique cycle stuff...)
Bulldogger