Welcome to the Z forum! What color is your Z?
You most likely have hazing built up on the headlights (they are 10 years old!) and can use a number of off-the-shelf headlight restorations kits available. Tape off your bumper, hood and any additional areas of paint and go to town wet sanding the headlights to remove the blemished finish. Example of an available kit:
https://www.amazon.com/CERAKOTE-Cera...4086464&sr=8-7