Ender dragon would be very simple but just a very long list of fill commands centred on the dragon =P Probably not the best idea either.
The only way I could see to make a performant method of doing would have been to check for creepers about to explode and then turn off mobGreifing for a moment while it explodes, then turn it back on again. Unfortunatly without detection of this it becomes tricky. It would be possible to turn off mob greif when a player is near a creeper, but that is far from ideal and not something I (dunno about zed I would assume not) would want to actually use.