Running the updated assignment rules in Planning State and viewing the accounts on the territory detail page is the best way to show sales operations what the data will look like after changing the territories.
Assignment rules are rules that determine how accounts are assigned to territories based on criteria such as account fields, address fields, etc. Planning State is a mode of Territory Management that allows users to preview how changes to territories or assignment rules will affect account assignments before activating them. The territory detail page is a page that shows information about a specific territory, such as name, description, users, accounts, etc.
By running the updated assignment rules in Planning State, sales operations can see how accounts will be reassigned to new territories based on the ZIP codes. By viewing the accounts on the territory detail page, sales operations can verify the accuracy of the account assignments and make any adjustments if needed.