Clustering
From Documentation
ZK components, pages and desktops are all serializable, so using ZK in a clustering environment is straightforward. However, it is a challenge to develop a sophisticated application that is ready for clustering. If you are not familiar with it, you might refer to J2EE clustering and other resources.
Here we discuss how to configure ZK for a clustering environment, how to configure some servers, and the important notes when developing a clustering-ready application with ZK.