MultiZoneUpdate presumes that there's a single place where all the zone to be updated are known. This is not necessarilly the case.
I'd like to see something like:
private ZoneUpdater zoneUpdater();
The main point here is that different event handlers would all be able to invoke ZoneUpdater.update() .
This would also allow a single response to render main content (for the requesting Zone on the client) plus zone updates to named zones.