Archives (Zip, Rar...)

OC supports compressing/uncompressing (extracting) files to/from common archive file types through built-in (referenced) open source 7zip library. 

You can check their licensing terms in the \Licenses\ folder.

It is still recommended to install 7zip standalone (64-bit) that integrates in the context menu. Managing archives through a separate program is faster because it is managed as a separate process (independent from OC) that can properly use computer processor threads just for compressing/extracting process.

OC doesn't support browsing the contents within the archives. The program can only navigate actual filesystems. 

File compression started as a way to just allow fitting large files into small mediums like floppy disks, but their largest utility is archiving all parts of the project for easier and faster moving, and are not intended to be used as interactive containers pulling the individual files out (opening a file from a packed archive requires extracting it to a temporary location, so it is not suitable for sensitive files)

For that purpose I suggest using file containers instead of archives using VeraCrypt or Cryptomator (With installing Dokan 1.5 (not 2!) for auto-refreshing contents of the mounted drive) which offer ability to create encyrypted file containers that act like a single-file archive, but they can be mounted as a new drive letter (not read-only like .iso), so they can be browsed like any other drive, copy/move/open/rename/delete files through standard file operations, and don't use temporary file locations when opening files from within, making them suitable even for sensitive files.