It's surprising how difficult it is to find a simple, concise answer to this question:
Or you could parse the log file if you don't need the data in realtime.
grep foo.zip /path/to/access.log | grep 200 | wc -l
In reply to comment:
The log file also contains bytes downloaded, but as someone else pointed out, this may not reflect the correct count if a user cancels the download on the client side.