By default, ZK creates components based on what are defined in a ZUML document, when loading the document. However, we can defer the creation of some sections of components, until necessary, such as becoming visible. This technique is called load-on-demand or render-on-demand.
For example, you could split a ZUML document into multiple, and then load the required ones when necessary. Please refer to the Load ZUML in Java section for how to load a ZUML document dynamically.
It improves the performance in both the server and client sides. It is suggested to apply this technique when appropriate. ZK Loader provides a standard on-demand evaluation called fulfill to simplify the implementation.
Load-on-Demand with the fulfill attribute