Exporting of .argo files to .zargo is a standard workflow using Argo UML modeling software. It represents export of projects (.argo) to final model file (.zargo). This can only be done using the original software and we know about no other 3rd party utility capable of this conversion.
Convert ArgoUML project file to ArgoUML model file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert argo to zargo on Windows
A UML modeling tool
Convert from argo file format
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.