ZK caches the parsed result of a ZUML page and re-compiles it only if it is modified. In a production system, ZUML pages are rarely modified so you can prolong the period to check whether a page is modified by specifying file-check-period in WEB-INF/zk.xml as shown below. By default, it is 5 seconds.
<desktop-config> <file-check-period>600</file-check-period><!-- unit: seconds --> </desktop-config>