According to our document Executions.schedule() should update UI asynchronously. Since ZK 6.5.1, the EventListener registered to Executions.schedule() API won't update UI unless another request is sent back to server.

Reproducible sample: http://zkfiddle.org/sample/1q1li3q/4-Another-new-ZK-fiddle
Please run the demo in local machine and use Servlet3 Comet Server Push.