We are using ZK for our web interface and it works out great using our in house EJB3 services.
Using the CommandServiceBean inteface I have run into the problem of having no way of setting the actor id to the current user. This makes it impossible to find out who is working on what at a given moment. But using the CommandService interface allowed me to run the ready made jBPM app incuding the jbpm-console that has helped a lot with troubleshooting while developing ZK pages.
Is there another way to hook into a jBPM engine while retaining the packaged application and web console?