Susan,
That is a very nice control panel.
Rudy,
All of the folks above gave great advise.
Here are a few pictures of my control panel and the Z 1000 controllers.
I ran a bus line connected to the B or C terminal of a ZW to all points of the layout for powering the Z1000 switch machines. Terminal strips are connected to the bus in areas where there is a cluster of switch machines. As mentioned above the switch machine red wire will go to the terminal strip / bus.
For making the run back to the control panel for the other two wires I found that using 8 conductor irrigation control cable with 18 AWG solid wires worked the best. Each cable run can be used to wire 4 switches to the controllers in the panel. Just make sure the green wire on the switch machine ends up connected to the green wire in the controller, and the yellow wire on the switch machine ends up connected to the white wire on the controller. The black wire on the controller goes to your common ground. Since I had over 50 switches to wire I placed terminal strips in the control panel for connecting the black wire from each controller to ground. The terminal strips in the pictures with the white wires are the ground terminals.
The Control Panel
Inside the panel.
I used white wire for the color of all comon ground wires on my layout. The lights on the control panel are also grounded to the comon terminals with the white wires.
I hope this helped.
Richard