Is there an event which fires when you go into a new zone (ie, through a loading screen)? I've found EVENT_ZONE_CHANGED which only seems to fire when you enter or leave POI areas, and EVENT_ZONE_UPDATE which I can't find the firing criteria for at all, but nothing for actually entering a new zone (ie, firing for a change of ZoneId or ZoneIndex). Also, what's the difference between ZoneId and ZoneIndex? More functions seem to use the latter.
This event only fires when loading screen happens. Sometimes it may fire when loading screen pops while you move inside a well crowded zone. It won't fire when you cross zone/subzone map though.