I'm not sure if that's worse - it changes the value from "" to "1" but it's applied only when `body.style.zoom` exists so it doesn't screw with Firefox.

I'm not the one to decide here but, to paraphrase, I'll keep the change unless you feel strongly about leaving the check out. :)

BTW, as for the line you linked to: wouldn't it be better to change `typeof div.style.zoom !== core_strundefined` to `div.style.zoom != null`?