Salesforce Trailhead Challenge: Create a validation rule to check that a contact is in the zip code of its account

Salesforce Trailhead Challenge

Create a validation rule to check that a contact is in the zip code of its account.

To complete this challenge, add a validation rule which will block the saving of a new or updated contact if the contact is related to an account and has a mailing postal code (which has the API Name MailingPostalCode) different from the account’s shipping postal code (which has the API Name ShippingPostalCode).

Name the validation rule Contact must be in Account ZIP Code
A contact with a MailingPostalCode that has an account and does not match the associated Account ShippingPostalCode should return with a validation error and not be saved
The validation rule should ONLY apply to contact records with an associated account. Contact records with no associated parent account can be added with any MailingPostalCode value. (Hint: you can use the ISBLANKfunction for this check)