Consider:
sef% mdfind 'kMDItemDisplayName =[c] "Zoom.us"'
sef%
sef% mdfind 'kMDItemDisplayName =[c] "zoom.us"'
sef%
vs
sef% mdfind 'kMDItemDisplayName == "zoom.us"'
/Applications/zoom.us.app
(Using '==' vs '=' doesn't seem to make a difference.)