Hello Kanna !

First of all, you need to know the rules how to check the given Zipcodes and then apply it to the settings of the Zipcode fields in the Studio->Forms->Persons->Add account, add a new field there, set it as "Mandatory" and set the "Check for " field as a regular expression. Below you may enter the reg expression itself. If it requires more complex checks then it will require the code's changes in the modules/boonex/persons/classes/BxPersonsFormsEntryHelper.php file.