It has a command board already. Your issue is not running it in command. If you dump 18 volts to that in conventional, it will go through the wall.
You might want to check out the TMCC board to find out how to add command to your ZW. I have CAB-1's, Power Master's and one Command Base - these are the original TMCC components introduced by Lionel. Now there's CAB-2's, and I don't know what else, because I've been out of the new loop for a while.
Fred