If the password is maintained inside the file itself (as per ZIP) then we won't even know it is there and just backup the file as a file.
Think of it this way - if you can copy the file from one volume to another without entering the password than Backup Exec will be able to back up and restore it as we do not care what happens inside the files (unless it is something like EDB, VMDK or VHD so protected by GRT anyway)
Full Backup of ZIP file happens, but Incremental/Differential does not backup the file even when there are changes. Does Backup Exec do an Incremental/Differential backup of ZIP files ?
Not sure why you havs started a new topic about Incremnetal and differentila backup of ZIP 9hwne teh topiuc was abotu passwords)
Backup Exec does incremental and differentil backus based on file level changes. As such if the archive bit or modifed time changes on a ZIP file we will back it up (depending on which method you have set to use) if it is not doing this then you need to look at whether the file is being held open so not recording the change until it is closed and/or whether the archive bit or modified time are changing in NTFS.
As an aside Backup Exec looks at file level on NTFS (so cannot look at individual changes inside the ZIP file for incremental or differential backups - basically if the zip file content changes the whole file is backed up again.