ZK supports Servlet 3.0 Pluggability, so you don’t have to configure ZK’s servlets and listeners in WEB-INF/web.xml at all. (Make sure you include zkwebfragment.jar)

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <description><![CDATA[My ZK Application]]></description>
    <display-name>MyApp</display-name>
</web-app>

On the other hand, if metadata-complete=“true” was specified in WEB-INF/web.xml (i.e., the support of pluggability is disabled), you have to configure ZK servlets and listeners manually as described in the Sample of web.xml for Servlet 2.4.