Zytel is one of those very difficult to bond polymers like PP, TPE, or TPO. The special repair adhesives that you can buy are usually expensive, and not very strong. Plastic welding often works very well if you have some of the correct plastic rod to use as filler rod. I have a couple soldering guns reserved just for plastic repair because I got tired of wasting money on the expensive special adhesives. You can read about a few methods recommended by DuPont on pages 112-113 of this pdf file:

http://www2.dupont.com/Plastics/en_US/assets/downloads/design/232409d.pdf

Or, sometimes you see one of these Remington Nylon 66 plastic stocks for sale on E-bay.