I have read that a few of you tried to add a zipper to the bow tucks. I did too, and thought I would share my technique. It is not perfect. Just before the step to sew the two inside pieces together, I added in my zipper. I sew a folded piece to each side of the zipper with the raw edges to the zipper.
Marked 1 1/2" down from top
Lined up zipper unit with mark & sewed 1/4" from fold
Repeat for other side.