I'm also having trouble with this challenge. With the logic below I get the error "The validation rule failed to enforce the business logic". But when I leave out the NOT (ISBLANK( checks for MailingPostalCode or Account.ShippingPostalCode I get a worse error "FIELD_CUSTOM_VALIDATION_EXCEPTION". Here's what my rule looks like:

I'm also having trouble with this challenge. With the logic below I get the error "The validation rule failed to enforce the business logic". But when I leave out the NOT (ISBLANK( checks for MailingPostalCode or Account.ShippingPostalCode I get a worse error "FIELD_CUSTOM_VALIDATION_EXCEPTION". Here's what my rule looks like:

I'm also having trouble with this challenge. With the logic below I get the error "The validation rule failed to enforce the business logic". But when I leave out the NOT (ISBLANK( checks for MailingPostalCode or Account.ShippingPostalCode I get a worse error "FIELD_CUSTOM_VALIDATION_EXCEPTION". Here's what my rule looks like: