Querying XML nested nodes
You can add an additional CROSS APPLY to break out the rows in the way you require:

SELECT  T2.lin.value('(./dLin/@Id)[1]', 'int') Id,
        T2.lin.value('(./dLin/@CoArt)[1]', 'varchar(20)') CoArt,
        T2.lin.value('(./dLin/@CoArtCust)[1]', 'varchar(20)') CoArtCust,
        T2.lin.value('(./lastOrd/@Id)[1]',  'varchar(20)') lastOrderId,
        T2.lin.value('(./lastOrd/@QtyLastOrd)[1]', 'decimal(18,2)') QtyLastOrd,
        T3.lin.value('(./dIni/@Date)[1]', 'date') DIni,
        T3.lin.value('(./dEnd/@Date)[1]', 'date') DEnd,
        T3.lin.value('(./uni/@Qty)[1]', 'decimal(7, 2)') DIni
FROM    txml
CROSS APPLY data.nodes('/order/lin') as T2(lin)
CROSS APPLY T2.lin.nodes('pLin') as T3(lin);


I had to guess the datatype for DIni, correct as required.