Here is a syntax that worked for me in the Target field of the shortcut as discribed above:
%APPDATA%\Zoom\bin\Zoom.exe "--url=zoommtg://zoom.us/join?action=join&confno=123456789&pwd=123456789&zc=0&browseer=Chrome&uname=John Doe"
Mind the space between ... Zoom.exe and "--url=...
Of course: use proper MeetingID and pwd.