You've checked the servo motor controller, and the servos, you'll now connect the motor controller up to the Raspberry Pi and make sure you can control the servos from it. Remove the USB cable from the PC and connect it to the Raspberry Pi.

Let's now talk to the motor controller by downloading the Linux code from Pololu at www.pololu.com/docs/0J40/3.b. Perhaps the best way is to log onto your Raspberry Pi Zero with putty, then type wget to get the latest download from the site. Then move the file using mv maestro-linux-******.tar.gz\?file_id\=0J315 maestro-linux-******.tar.gz, where ******* is the current version number of the file.

Unpack the file by typing tar -xzfv maestro-linux-******.tar.gz. This will create a directory called maestro_linux. Go to that directory by typing cd maestro_linux, and then type ls -l. You should see something like this:

The README.txt document will give you explicit instructions on how to install the software...