Teaching How to Open and Close Fasteners

It is generally easier to open fasteners than close them, so I suggest starting out opening as many objects with fasteners as possible to develop coordination  between the hands especially to stabilize with the nondominant hand. I often ask my very young hippotherapy clients to help me get out my sunglasses by opening and then zipping closed the case shown below. This photo shows anactivity I made that involves opening buttons, a buckle,snap and zipper to find the toy horse.

I suggest teaching how to close a zipper by having the child stand up wearing a jacket with a pretty large zipper. Stand behind the child so that you both have the same perspective. The jacket is easier to manipulate while standing rather than bunched up on the lap.   
Zipping is complex so I suggest using the backward chaining teaching method. this involves teaching the last step first. Consider attaching a cute toy or pin to the zipper tab to make pulling up easier. Then YOU connect the zipper together and place the child's nondominant hand to pull down on one jacket side while the other hand pulls the zipper upward.

After success with this step work on connecting the zipper into the slider part that zips by using the hand-over-hand method. You may consider color coding the two sides so that you can say "pull down the red jacket with this hand" and "pull up the blue zipper with this hand". Be sure to do all of this when the child is feeling rested, happy and then reward for trying with a favorite activity.

 Dressing and undressing dolls and other toys with fasteners is a good supplement to working on using fasteners that the child is wearing.