You do not need to pay any attention to your damper if you are decreasing the travel to more than what it is now, because the damper will just compress to accomodate for the decreased travel. Yes, you can even decrease your 180mm fork all the way down to 130mm and your damper will simply compress to the new travel without any negative effects.
However, if you are increasing the travel of your fork, then you need to check to ensure that you are not going above the maximum travel of your specific damper. Below is a list of the common dampers that fit in the Fox 36 Rhythm/Marzocchi Bomber Z1 chassis, along with their maximum travel according to the fork's wheel size:
Maximum Damper Travel (DO NOT EXCEED):
- GRIP2 Damper Maximum Travel : 29" Fork = 170mm / 27.5" Fork = 180mm
- GRIP Damper Maximum Travel : 29" Fork = 170mm / 27.5" Fork = 180mm
- New 2020+ FIT4 Damper Maximum Travel : 29" Fork = 170mm / 27.5" Fork = 180mm