Instead of just taking in the waist at the side seams, I added darts front and back for a more graceful transition from hip to waist. Her fullness at the hip falls at her upper thigh, so her hip curve didn't match the pattern's. I took in the upper hip and added a bit to her thigh area.
It's pretty easy to place the whole zipper on the surface of the garment in a seam, but I didn't want the zipper tape exposed. I looked everywhere for a good method and if I wanted to just put it in anywhere on the skirt that was pretty easy, but how to do it in a seam, that I had a hard time finding. I made samples and I faced the seam so that I had finished edges around the zipper teeth and a clean transition to the remainder of the seam.
Here's a closeup of the zipper.
She is very happy with the results and she proudly tells all her friends that her Mom made it.