To setup the 4k Firestick remote follow these steps below.

Go into Settings -> Sound & Display -> HDMI CEC Device control On

Settings - > Equipment Control - > Add new Equipment - > Soundbar- > Search ZVOX or it may automatically detect and play audio through the ZVOX.  

Confirm the Volume up, down, Mute and Power work on the remote and you are all set.

These instructions are for the firestick remotes with the IR sensor, volume, mute, power buttons.