Does it have to be a single SQL statement. The best (and easiest) thing to do is to store the inner SELECT into a cursor and querie the outher one on the cursor like:
SELECTSUM(addlog.tran_bal) AS TTotal, SUM(0) AS PTotal
From Addlog ;
UNION ;
SELECTSUM(0) ASTotal, SUM(eftlog.tran_bal) AS PTotal
FROM eftlog ;
INTOCURSOR x
SELECTSUM(TTotal), SUM(PTotal)
FROM x ;
INTOCURSOR Result