first copy and paste the edge line from the middle of the shirt this will keep the contour shape from the shirt
make a new straight line add add more points if needed then do equal-spaced-points blip.tv/file/1921540
now use the bend tool from the equal spaced point line and bend it to the contour shape, now you have the contour shape with equally spaced points the equal-spaced-points will keep the zipper metal parts equally spaced all so.
make 1 head shape for your metal zipper now take that shape and use copy on support to your new line i just moved the shape around and copy on support again to make 2 copys then off set the copys