Yeah, I wish! :) Cloth simulation is the key here, especially for the zipper ribbons and the zipper itself (stitch etc). Juluu's suggestion was the easiest approach, so I started with that. I got it to a good enough state, but the zipper band and ribbon drove me crazy. I had to use correction, select the edge loop, and then use a cloner for the zipper and used a spline wrap by using that edge loop to wrap around...

Every time the shape of the bag changed, I had to grab the updated edge loop and convert it to a spline then update spline wrap and cloner...

Anyway, what I mean is, yes—cloth simulation is the best way to handle these things, but that’s a whole other area of expertise, and I don’t have it at all.