1. run the installation and it appears to install correctly (ZoomOutlookPluginSetup ran from c:\temp)
2. installation folder was set as default C:\Program Files (x86)\Zoom\Zoom Outlook Plugin\
3. options to add meetings appear in outlook 2016 calendar.
4. noticed that plugin files are actually installed in the root of c:\
5. tried forcing installation in other folders but these are always ignored and files install off c:\
6. now see issues with Zoom dialogs and a message about "plugin_launcher.exe is using ntdll.dll from an unknown publisher. are you sure you want to run this software" after that follows a number of dialogs citing plugin_launcher.exe)
i am a domain user and the computer my documents is mapped to a network drive. solved this issue by creating a new local user with admin rights and logging in then installing the plugin so it now installs in the correct folder and error messages have gone away.