sorry I misread your question
If I got it right this time
something like the following should do it

...
FROM allzones A ;
   LEFT JOIN p_ccnt B ;
         ON ((a.iID = b.iZoneID) and (a.category=b.category));
   LEFT JOIN p_tcnt D ;
         ON ((B.iID = D.iZoneID) and (b.Category=d.category)) ;
   LEFT JOIN d_ccnt C ;
         ON ((a.iID = C.iZoneID) and (a.category=c.category)) ;
   LEFT JOIN d_tcnt E ;
         ON ((C.iID = E.iZoneID) and (c.category=E.category)) ;