It's not quite clear what you mean or what you want to happen exactly. When you say "zoom" do you mean resizing the layout via the browsers zoom function or were you just referring to the window being opened and closed?
The elements will wrap at small window sizes so you would be better using display:inline-block instead of floats so that they don't snag. Also give them a bottom margin to stay clear.
e.g. (this code is additional to yours and not a replacement)
*display:inline;/* ie6/7 hack for inline block*/
I also added a min-width because you are not scaling the images so the images will stick out unless you stop them.