Perhaps your 16 includes spaces. If they are all the same, you could include
the spaces in sumproduct, or you could use the trim function to remove the
spaces, or use paste special to multiply column c by 1 to convert to a number.
=SUMPRODUCT((D1
1000=0)*(C1:C1000="16 "))
if your cell contains 16 followed by two spaces
=SUMPRODUCT(--(D2
1000=0),--(C2:C1000="16"))
if your cell contains only 16 in text format
=SUMPRODUCT(--(D2
1000=0),--(C2:C1000=16))
if you convert 16 to number
You would want to do the same sort of adjustments if it's possible the 0 is
not an actual zero as well...
good luck!