Both .iwp and .iwzip are projects from Website X5 software and perhaps some of its other version, so this will be you best shot for handling this particular conversion. However, we could not find any specific information about this conversion or if its actually possible or useful to do so.
Convert Website X5 project to Website X5 project.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert iwp to iwzip on Windows
A fully featured software for creating websites
Convert from iwp 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.