It depends on the firewire interface that you have. The FirePod is a very oldschool firewire interface and was great in its time, but it does not support the Z latency feature.
The Zero Latency feature is ONLY available in Studio One and works with the AudioBox 1818VSL, FireStudio Project/Mobile, and the Studio 192.
You need to create 2 or more output busses in Audio I/O Setup and check the box for Cue Mix. Then in the Console Mixer view, you can click a Z button for the Cue Mix of any audio channel. The Z will be located just to the left of the padlock button for the Cue Mix.