Both .hmxz and .hmx files are projects from Help & Manual documentation tool and content management system and if any program can somehow convert them, it would be this one. It looks like you could perhaps save one to another using the standard File ► Save as.. function found in the program.
Convert Help & Manual help file compressed XML project to Help & Manual help file project.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert hmxz to hmx on Windows
Help & Manual is a documentation tool and content management system for both single and multi-author editing. While it is as easy to use like a normal word processor, Help & Manual gives you the full power of a true WYSIWYG XML editor.
Convert from hmxz file
to hmx file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.