The video below shows 3 different individuals zipping closed and inserting into a container. This adds a new twist to the usual insertion task.
I put flower designed duct tape on the ends that needed to be grasped and a piece of pipe cleaner through the zipper slider with a round piece of plastic attached to grasp.
I think that pulling them closed not only develops some nice bilateral coordination and a strong grasp but prepares them for the functional skill of pulling the small zipper slider tab or grasping an adapted zipper with a larger tab to pull (like the green ones in the photo).
There is also a certain sensory quality to it pulling them closed. It is quick and they don't rip when pulled hard so the individuals can feel an immediate sense of accomplishment.
After closing each zipper, I helped them push it through an opening in the large container so that they perform a 2 step task. I used the words "Close and push inside" . The gentleman in the photo was feeling a bit agitated but he loves to use his hands. So he is sitting in a rocking chair covered with soft material with a pink vibrating cushion on his lap while closing the zippers.
I chose to teach him only to close them. It seems like an easier skill than opening the zippers and then they fit more easily into the container opening when closed.....