A VAT breakdown (BG-23) with VAT Category code (BT-118) "Zero rated" shall not have a VAT exemption reason code (BT-121) or VAT exemption reason text (BT-120).
/*/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[normalize-space(cbc:ID) = 'Z'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']not((cbc:TaxExemptionReason) or (cbc:TaxExemptionReasonCode))