File managers like windows explorer and xplorer² can browse into .ZIP archives to examine the compressed files therein. So theoretically they should be able to read into JAR and DOCX "archives", and read the contents that make up a Java program or a Word document. I am not sure why anyone would want to do this, but let's assume that you actually want to peek inside, and move on with the demonstration :)
A possible use could be searching for something by name inside a pseudo-archive
One way to make this happen would be to edit the registry where document types are declared, and make JAR and DOCX behave like ZIPs, e.g. make HKCR\.docx point to CompressedFolder type, just like ZIPfolders. This will make such documents folder-like browsable, but then it would be harder to open them with their native application, say Microsoft Word.
xplorer² ultimate edition offers a different path for those that wish to enter disguised zip files without altering the default type associations, through Total Commander WCX plugins. If you install something like Total7zip you can enter JAR and the like with File > Enter archive menu command. Using WCX plugins with xplorer² isn't very difficult if you know how to do the association, and here are the detailed steps:
ps. To any orthodox readers out there, happy easter / Χριστός Ανέστη!