An EAR file could have multiple WAR files. Each of them is a Web application. There are no standard way to communicate between two Web applications.

However, ZK supports a way to reference the resource from another Web applications. For example, assume you want to include a resource, say /foreign.zul, from another Web application, say app2. Then, you could do as follows.

<include src="~app2/foreign.zul"/>

Similarly, you could reference a style sheet from another Web application.

<style src="~app2/foreign.css"/>

Note: Whether you can access a resource located in another Web application depends on the configuration of the Web server. For example, you have to specify crossContext="true" in conf/context.xml, if you are using Tomcat.