The VAT category tax amount (BT-117) in a VAT breakdown (BG-23) where VAT category code (BT-118) is "Zero rated" shall equal 0 (zero).
/*/cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[normalize-space(cbc:ID) = 'Z'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']xs:decimal(../cbc:TaxAmount) = 0