Work with Existent Servlets
From Documentation
This documentation is for an older version of ZK. For the latest one, please click here.
By enclosing ZUL components with FORM, you could post the content of ZUML components as the request parameters to an existent servlet. Refer to ZK Developer's Reference: HTML Tags for details.
With this approach, you could design rich user interfaces without modifying the existent servlet by simply replacing some of them with ZUL components.