Can plastic zippers be fixed?
Answers:
You probably need a new zipper: If you have never worked on them before, get someone else to do it for you. Difficulty would depend on the type seam and waistband. With a waistband it is a little more complex because you would need to remove both ends and then reassemble it after you sew in a new zipper. Relative to the price of a pair of good pants, a zipper does not cost too much.
If you really can't do it yourself, even though there is no waist band, take it to a seamstress. Ask at your local laundry/dry cleaners which usually have seamstresses. This is where they do alterations (shorten hems, sleeves, etc.) and clothing repairs. I had several jacket sleeves shortened and ithe price was reasonable. If you have a tailoring shop nearby, take it to them and ask "how much?
Plastic zippers are not durable and for that reason I would recommend that you change it. When I've "fixed" them in the past, I've experienced that it snags or splits open again very soon -- so it isn't worth wasting time fixing it.
Other answers:
Take the zipper out and put in a new zipper. Or take to a person who can fix at the cleaners
Take the zipper out and put in a new zipper. Or take to a person who can fix at the cleaners