What do I want to do?

I would like Firefox to save files with the .pages extension as .zip files automatically.

Scenario

You are browsing through your emails and you notice your friend just sent you an email with a file attached (a .pages in this example). Unfortunately, you have a laptop that runs Windows. Your friend continues to send tons of emails with .pages files attached and you are tired of manually saving the files as a .zip file.

Ultimately, you would like Firefox to be set up so that the download/file manager recognizes the .pages extension and automatically converts it to a .zip file.

What have I done?

I have saved files manually by selecting save as "All Files" and setting the extension to .zip. I've gone through Firefox and their documentation and have not found anything on how to complete this task.

Why am I doing this?

1. To save time (only a few seconds, not the main reason).
2. I would like to setup a simple solution that "converts" a file automatically without having to recall steps on how to achieve the task manually (for clients who aren't exactly tech savvy).
3. So that clients with Windows can access the files.

IMPORTANT NOTE:

I am not trying to save the web page, rather an Apple document equivalent to Microsoft Word.

UPDATE:

The really easy method would be to save one file, right click it, choose properties and open all .pages files up with WinRAR (or any other program that extracts files from a compressed folder). For the sake of learning, I am going to "neglect" this method and continue to do some research on Firefox add-ons. I would still like to have Firefox or the download manager to do the bulk of the work for converting the file.