I created a beta version of the Asterisk PBX Integration Zimlet that should work with ZCS 6. My dev machine was ZCS 6.0.1. Due to changes in JSP handling in ZCS 6 you need to create the following symlinks in /opt/zimbra/jetty/webapps/zimlet/WEB-INF
For updates you should remove /opt/zimbra/jetty/webapps/zimlet/WEB-INF/lib/asterisk-java-1.0.0-m2.jar manually.
zimbra.tld -> /opt/zimbra/jetty/webapps/service/WEB-INF/zimbra.tld
lib -> /opt/zimbra/jetty/webapps/service/WEB-INF/lib