If you are going to model the zip as an object, it should be put in the rigid redorated group. Then it will move with the dress but not lose its shape. As explained above, even this is not a good idea. Put the zip in the texture and give it depth with displacement, saving yourself a lot of headaches.

Poser 11 Pro, Windows 10

Auxiliary Apps: Blender 2.79, Vue Complete 2016, Genetica 4 Pro, Gliftex 11 Pro, CorelDraw Suite X6, Comic Life 2, Project Dogwaffle Howler 8, Stitch Witch