Vital.......If you are using the supplied overdraw shelf assembly check 2 things.
1. Make sure the shelf section is sitting tight against the riser.
2. Make sure that the Overdraw " arm" (The section that extends along the shelf) is NOT flush against the bows arrow shelf. When the bow is fired this arm is flexible and vibrates rather violently(lay your finger on it for a shot and you will see) if within this vibration it is close enough to contact the arrow shelf you will get a pretty nasty noise.

Also make sure there is not any " Play" in the main swingarm. There is a fine line between too tight and too loose, This arm should move freely but not " Freefall" when adjusting it.

These are the only suggestoins I have as " Ausie" hit on the other 2 potential problems....especially the axle shim at the connection between the slide and the turnbuckle sleeve. SOme of the ZE' s I' ve seen have been sloppy at this junction.

Good Luck.