e.g. I have
div.style.zoom = 1.2
Typically You cannot remove properties from built-in objects like that, and certainly not in IE (the zoom attribute of the style object is a IE extension)
You can set it to the default value:
el.style.zoom = "";
the effective zoom will now be whatever follows from the definitions set in the stylesheets (through link and style tags)
So this syntax will only modify the local style of this element.