var divs = map.getContainer().getElementsByTagName("div");Now variable 'zoomInButton' is the container of 'Zoom In' button and you can change its style or construct an event listener.
for(var i = 0; i<divs.length; i++)
var title = divs[i].getAttribute("title");
Update 2008. Excpected lifespan of this kind of hacks is a few months. This hasn't been working for a long time. if(title=="Zoom in") works but but you have to lock the language to hl=en.