Can I add the same website address to both local and trusted site zones?
Great question and the answer is No. You can have one URL(Same Exact) per Zone and if the Site already exist on another Zone, lets say you had it in the intranet zone and now wants to add it to the trusted site zone a warning should come up.
Here is a sample scenario you can test:
Add the https://domain.com site to the Local Intranet zone in IE.
Screenshot:
Now, try adding the same https://domain.com site to the Trusted Site Zone. A warning will come up.
The site you specified already exist in the local intranet zone. Would you like to move it to the Trusted site zone?
What if I used the Site To Zone Assignment List GPO to push this, what will happened? Same answer, No.
A warning will appear:
The name "https://domain.com" has already been specified. Make sure that you specify a unique value.
