You’ll need to go to the Play Store App, and open up ‘My Apps’. Once there you can find Zombies, Run! in the ‘Downloaded’ or ‘All’ tab. Tap on Zombies, Run!, and you'll be able to click 'Move to SD card'. The button will first show 'Moving', then 'Move to phone' once the move is completed. You'll now find the app listed under the 'On SD Card' tab.
Unfortunately one of the files cannot be moved and must be installed to your phone’s internal memory. Because of this it’s normal to see some Zombies, Run! files still on your phone’s internal memory.
Please note: You must have a physical SD card in order for this process to work.
Some phones do not have SD card slots, but may call part of the hard drive ‘SDcard’. Because this is not a physical SD card, you will not be able to move Zombies, Run!.