Files with extension tgz are gzipped tar-archives.
Files with extension zip are pkzipped archives.

Both should be manageable with most modern zip-tools.

Computers running older versions of MsWindows and Macintosh operating
systems, don't come with these utilities pre-installed. However they
can be downloaded from:

http://www.winzip.com/                  (windows)
http://www.stuffit.com/                 (mac)

Presuming a user with management permissions and rather elementary
computer skills, the downloading, installation and usage of such a tool
is completely straightforward.