So I will share a secret with you. It's probably not really a secret, but it's fun to say it is. My mother taught me this sewing secret. I'm sure if you have ever sewn you know the mind breaking horror and frustration that can come with putting in a zipper, especially an invisible zipper. If you don't, consider yourself lucky and believe me when I say they are evil.
Invisible zippers are tricky at best, even now with as many as I have put in to date, I still will almost always put one side in backwards the fist time around. There is that and if they are just pinned, they can slip and move and be a pain. So my mother taught me to pin first and then go in and baste that sucker down. I works remarkably well! Some of the girls at school didn't even realize there was a zipper in my side seam until they saw the pull dangling at the top.
My own trick after basting is to use a regular zipper foot to sew it in and not an invisible zipper foot. I tried in class when they taught us to use a invisible zipper foot, and it had disastrous consequences. I find if you move your needle position over almost as far as it can go (but not all the way over) there will be a millimeter or two between it and the edge of the zipper foot, and that extra distance between foot and needle will bend over the edge of the invisible zipper and get a closer stitch.