Many flags are not working, for example;

NoDeploy -  (Item breaks if a player tries to deploy something, or place a lock on an item)
NoNPCSpawns - Animals still spawn in the Zone with this set.
NpcFreeze - Animals still are able to move and attack players

There may be more, though these are just the ones I've ran into.

Good luck.  This plugin should've been turned over a long time ago.  Instead, it hasn't and, though updates continue with the game itself and Oxide, this plugin remains unmaintained.  There are lots of good plugins on this site that need revamped.  Best to look somewhere else where the plugins are better maintained.

Fixed in the upcoming version. There is a beta of it out for testing if interested 
https://umod.org/community/zone-manager/44117-310-beta