The Zero Factory: Double Shift | Guided Math Lesson | Gr 4 | Digital + Printable Bring math to life with this story-driven guided math lesson featuring Leo and Countdown! Students follow an engaging narrative set in the zero factory's second shift, where new combo machines multiply by 20, 30, 40, 200, 300, etc. leo learns that every combo machine is really just a basic-fact machine connected to a zero machine. while building deep understanding of the zero factory: double shift. What is Included