Silencer.scpt

property running       : False
property checkInterval : 30

on run
  tell application "System Events"
    if (exists application process "zoom.us") then
      running = True
    end if
  end tell
end run

on idle
  runningNow = (exists application process "zoom.us") 
  
  tell application "System Events"
    if running and not runningNow then
      set volume output volume 2
    end if
  end tell
  
  running = runningNow
  return checkInterval
end idle