In order to assign automated 2.1.12 Area Classification to all of your accounts you have to configure the correlation between zip code and code in the object area classification.

Please take note that the classification for alphanumeric postal codes (Canada, Netherlands, UK etc.) will not update the according accounts. If you would like to use the Area Classification for these countries please enter the Area Classification Name manually in the Account.

To configure the correlation between zip code and code go to the app launcher and search for area classification. Create new records for all your codes:

Enter 

A record with the following data 

will lead to the classification of 3a for this account: