This conversion basically represents repacking of one of the known Unix archives (.z) to 7-zip compressed archive (.7z). The easiest way to do this conversion would be to download 7-zip as it supports both of these file types and seems to be the obvious choice. But you can find other choices as well.
Convert Unix compressed archive to 7-ZIP compressed 7z archive.
We have found 4 software records in our database eligible for .z to .7z file format conversion.
Microsoft Windows software - convert z to 7z on Windows
Popular open source file archiver with a high compression ratio
Convert from z file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned z to 7z. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the many available file compression utilities
Apple macOS / Mac OS X software - convert z to 7z on OS X
Mac version of the popular utility
A backup and archive utility