The FBReader knows how to open zipped file. This is why you can open zipped *.fb2.zip file
FBReader can not, however, open *.doc file directly. For opening a *.doc file PocketBook uses a little Linux program called AntiWord.
If you wanted to open *.doc.zip file you would have to make a script called antiword that would unzip the file first and then run it through the built in antiword program.
This should be relatively easy to implement.
How much do you need this to be done?
*.doc files for versions of MSWord newer than version 6.0 the doc file is already compressed. For versions of Word before the 97 version you should be able to just rename the doc file to rtf file and zip it afterwards.