The examples shown at
http://www.zkoss.org/zkdemo/responsive_design
work partly on Chrome/Android:
scrolling of page areas works,
swiping to show/hide the sidebar do not, the sidebar is then displayed with a minimal width, but unusable

The demo apps are totally broken on Mobile Firefox/Android (no scrolling, side bar only by clicking button). I came to this test when searching for a solution or a hint regarding this problem:
http://tracker.zkoss.org/browse/ZK-2498

On desktop browsers, the examples work very nicely as far as I can see.