When I use save, I get the same download filename with .zip as I do in chrome.
First it asks do you want to OPEN or SAVE..
If you say SAVE, the filename has .zip on the end.
Then I changed the behaviour of FF so that doesn't ask where I want to save the files and instead use a default download directory (I normally never do this since I save content depending on what it is to different locations..
And I got the same response that you got. The saved filename has no .zip on the end.
Need to use my debugger to see exactly what the webserver is serving up for the filename to see if FF is just being too cute or not.
The setting I use if you care is:
Makes FF always ask and confirm where you want to save the file and does not mess up the filename (apparently).
That being said, I am not a big fan of the long number for a filename in the first place. I would always rename it to something that makes sense so I know what it is later. It is quite often for software to use a generic filename and not include the version number which I think is important.