I'm not telling you what to do, but this is how I organize my workzones...
First off, name them "Keepers - Animal, Animal & Animal" and "Vendors - Facility Name", etc. This seems to be the easiest way to name them so they stay organized in alphabetical order in your staff zone menu. For example, all of the keepers will be in a row and the vendors in another, just a simple way to stay organize. I must give Frontier credit for this as I think I saw it in a campaign zoo.
Secondly, I dont have workzones for every staff member in my zoo. I make workzones for keepers (usually 1 keeper per habitat animal and 1 keeper per 2 exhibit animals). Usually, I stick to around 3 habitats max in a keeper workzone. With vendors, I stick it to one "food court". For example, today I built my Caribou Cafe with 4 food/drink shops and assigned 6 keepers to it (3 vendors per every 2 shops). For research, I clump the mechanics and veterinarians together into one workzone. And finally for mechanics, I make a workzone named "Mechanics - Maintenance" and assign them to every habitat, vending machine, exhibit, toilet, and basically every facility in the zoo. Obviously, the bigger the zoo, the more mechanics you need in this workzone. As for educators, I usually do 4 or 6 animal talks and evenly place them throughout the "year". 2 educators for 4 talks and 3 educators for 6, and spread the talks out. For the security guards and caretakers, I dont assign them to workzones along with veterinarians that aren't for research.
As you can tell, I'm very organized and everything has to be even and symmetrical.
As for your situation, I haven't really played around with security guards and caretakers in workzones so I dont really know. If I had to take a guess, if you assign caretakers to certain staff rooms that means that they are only assigned to those staff rooms and wont do any of their other tasks. This may also apply to the security guards. Once again, I dont know if this is correct. Also, I dont know how big your zoo is, so I cant really understand where you're coming from.
Lmk if you need any more clarification or have any questions.
Hope this advice helps!