Yes, you can! Rather than type the instructions over again, I am going to give you a couple of web pages with instructions on how to do it.
The first of the links seems to be the most straight-forward. The others are for reference purposes.
Here is a Youtube video describing how to do it (if you can stand the music ^_^ ):
Please let me know if you need further assistance and I will be happy to keep working with you.
I just noticed you mentioned your version of WinZip has command line functionality. Does that also mean it has no GUI interface? Can you please give me the version of WinZip you are using?
WinZip can encrypt files using the AES standard. I am including a link to the knowledge base article that describes the process. I haven't found any specifics about spanning and encrypting, but I don't see why you shouldn't be able to. One suggestion is to encrypt files as you add them to the .zip collection rather than after. Here is the link:
Might I add that you should make copies of your original files and use the copies to zip. This will preserve your originals should WinZip behave differently than expected.
I am attaching a youtube video that addresses encryption and entering a password. Can you take a look at it and verify that you are seeing the same windows when trying to create this file? Another thing I would like you to try is to encrypt and password ***** a non-spanned zip file and see if the behavior is the same.
It looks like the link didn't come through. Sorry about that. I have two different youtube videos. Here they are again:
The first link was the one I sent last time.