Here is a simple flow that I just created.
What you'll need to get this to work is an extra action called "Upload to FTP".
It's free, so download it right here
http://www.automatorworld.com/archives/upload-to-ftp/
Import the action.
Then open up my small workflow.
Now you need to edit some of the stuff.
You need to enter your own ftp-host address, your username, and the password for that account.
You also might want to change the destination directory.
After that, save the flow as a plugin to the Finder so you can start it by rightclicking a file/folder.
There are a couple of issues with this workflow.
I haven't been able to set the filename to the original name with the extension zip.
It will always have the same name.
Thats why I added a "rename of finder-object".
The only thing I could think of to make each archive unique was to rename the file to todays date and/or time.
There is also an issue with the ftp-action, if the file exists at the ftp host the file is overwritten.
Anyway, hopefully you can use some of the flow and perhaps even build something useful.
If there is anything that I haven't explained good enought - just ask.