The third book in the Pete & Pillar Series, Mack & Zach tells the tale of two mighty dump trucks. Even though they are brothers, they are as different as night and day. Mack, arrogant and self-centered considers himself the strongest, best machine ever. His humble brother wants to find out what really makes a machine great. As a contest ensues, Mack is in the spotlight, but where is Zach? Will he find out what it takes to be great?