The element "Deliver to post code" (BT-78) shall be provided if the group "DELIVER TO ADDRESS" (BG-15) is delivered.
(/ubl-invoice:Invoice/cac:Delivery/cac:DeliveryLocation/cac:Address | /ubl-creditnote:CreditNote/cac:Delivery/cac:DeliveryLocation/cac:Address)[$supplierCountryIsDE and $customerCountryIsDE]cbc:PostalZone[boolean(normalize-space(.))]