Code:
With x as (SELECT W1AUF, W1FNE, W1PNR , SUM(W1VZT) W1VZT
FROM ZW1 
GROUP BY W1AUF, W1FNE, W1PNR),
 y as (SELECT W2AUF, W2FNR , W2PNR , SUM(W2MIN) W2MIN
FROM ZW2 
GROUP BY W2AUF, W2FNR , W2PNR),
z as ....  

SELECT SUM(W2MIN), SUM(W1VZT) ,    max(z-Auftrag)           
FROM x, y, z
WHERE W1AUF = W2AUF     
AND W1FNE = W2FNR 
AND W2PNR = W1PNR 
AND W2PNR = 36166 
AND W2DAT = 20121001
and w1-w2feld = z-feld      (natürlich die 'echte' verknüpfung)
and ....