"Romero's Hero" achievement hint
When first starting the Zombies Uprising mini-game, look around the beginning location. You will see a red arrow that has fallen and is pointing up and down leaning against a wall in the right back corner. Walk up to this arrow, then crouch and turn around and proceed to hold Away so that you keep moving into the wall. The zombies will not move at all. Use headshots to take out the smaller ones. When there is a shortage of zombies on the screen, get off the arrow for a couple seconds and use the opportunity to have the zombies respawn and to collect more ammunition. You can kill most of the zombies by doing this. You will have to find the last few, but the mini-game will be very easy.