I feel a little funny introducing a "new" way of working with an invisible zipper
but, here goes. This is what I do.
Step 1(no photo for this one)-
Fuse strips of interfacing about 3/4" wide and 2" longer than the zipper to both seam allowances of the center back of your garment. (Oh, by the way, it helps a lot if you iron the teeth of your zipper flat with a not too hot iron.)
Step 2-
Baste the two back pieces together as far as the length of the zipper being careful that the waist or bodice seams of both sides match.
Step 3-
Lay the zipper, right side down,with teeth along the joint of the seam.
Step 4-
Baste the zipper where the waist or bodice joins the skirt part of the garment to assure that the waistline or bodice seams are not distorted when you apply the zipper.
Step 5-
Starting at the waistline where you just hand stitched,sew the side of the zipper to the seam allowance while pushing down to flatten it against the fabric.Starting at the waist again, sew the top half of the zipper to the seam allowance. Repeat on the other side.
This is the zipper joined to the seam allowances.
Step6-
Take out the basting from the center back seam.
This is what you have on the right side now.
Now go ahead and apply your zipper using the special invisible zipper foot that came with your machine (right) or if you don't have one you can buy one of these (left) for very little money and it works just fine.
Because you have attached the zipper to the seam allowances, it won't move while your attaching it permanently and your joining seams at the waist will look like this...
Just an added note.You may have to play with the position of your needle to get the zipper to be "invisible.If it's not right the first time , try it again. It does take practice but it is so worth it. See!!
I hope these directions are clear. If they're not, please let me know and I'll rewrite.
Good luck. I hope this works for you.