How fun! I haven't seen any patterns like this, but this is how I would do it.
Start with a plain skirt with back zipper as the underlayer. Cut out the underlayer but don't sew anything yet.
Make the scallops as the overlayer. I have sketched what looks like the scallops of the skirt. My apologies for my drafting abilities - this is just a concept drawing.
It looks like you'll need about 9 or 10 of the front scallops; double that for the back ones. Be sure to cut scallops for both the left side and the right side of the front.
If you have a serger, serge along the bottom of each scallop to finish the edges. If you're using fabric that does not fray, you can skip this step.
Start layering the scallops from the bottom and going up, like putting a roof on a house. Once the scallops are in place, you can construct the skirt.
I'd love to see your finished product!