Unfortunately payouts to z addresses will remain disabled for the time being. We have tested paying out directly to z address using the latest Zcash version 1.0.4 but the system is simply to slow for large scale payments required by the pool. Paying to just 10 timers took between 7 and 15 minutes which is not suitable for paying out thousands of miners in a timely fashion. We will continue to monitor the Zcash developments and evaluate the feasibility with every new Zcash version.
Edit: All tests were done on a dedicated Intel Xeon machine with 32 GB or RAM.