I installed the Zoom client just to have a look for myself. The syscalls in question emanate from freshly forked processes that immediately execvp() the command `pidof` (on my system it finds it under /usr/bin, so it's the system command, not anything fishy shipped by Zoom). Actually, the command-line argument to the command is, in succession:
gnome-session
gnome-panel
gnome-shell
gnome-session-binary
ksmserver
cinnamon
cinnamon-session
mate-panel
mate-session
xfce-mcs-manage
xfce4-panel
xfce4-session
I suppose Zoom goes through the whole list on my system because it finds none of them. The fact that it stops on parent's system suggests that Zoom stops when it finds one. This hints at a very crude way to determine the desktop environment!