Welcome to the forum. I am not familiar with your KZ coach/trailer, but try the attached link listing the KZ manuals by year and type and pick the specifics for your rig. Look under the plumbing/fresh water/drains sections. Sometimes you get lucky and they will advise where to find the low point drains etc. Good luck with your Winterizing.
https://www.kz-rv.com/owners-manuals/