By just adding a couple of lines to the official Zopim Javascript snippet in the <head> section of your page, you can easily disable Zopim on mobile devices with small screens and really small browser windows. Sure, a few visitors won't be able to chat with you, but wouldn't you rather they be able to access your site?
Here is an example of the code which will disable Zopim on screens with a height or width resolution under 480 px. I've highlighted the two lines that you will need to add to your code:
<!--Start of Zopim Live Chat Script-->
<script type="text/javascript">
if (Math.min(window.screen.availHeight,window.screen.availWidth) > 480) {
window.$zopim||(function(d,s){var z=$zopim=function(c){z._.push(c)},$=z.s=
: : : : : : : : : : : : :
type='text/javascript';e.parentNode.insertBefore($,e)})(document,'script');
}
</script>
<!--End of Zopim Live Chat Script-->