If you need to protect a zip file by a password to send via email, then there is no way of doing with the standard “compress to zip” context option.
Instead, go to the command line and run the following:
zip -e nameofzipfile.zip filetoadd.txt otherfile.csv
This will create it for you. Probably needs a recent version of OSX though (I’m on 10.5.6).
