I have the following table:

A B C D
3 1 0.5 0
2 2 0 0.5
3 2 0 0
0 1 0.5 0
1 0 0 0
2 1 0 1
1 2 0.5 0
4 1 0 1.5

The formula required is to:
1) check if any row in column C has 0 (zero) and see corresponding cell in
column D also has 0 (zero). Table above shows row 3 and 5.
2) if matches, then check if (cell A - cell B) of the same row where the
above condition is true returns a positive value.
3) if a positive value is returned, then count it. Above example will return
a value of 2 (both occurences of 0 in C3 & C5).

Can anyone help?