Go from the starting area to the riverbank and use the two binoculars.

Look for a dancing zombie on a rock cliff and hold the position with the first binoculars until you exit the binoculars.

Afterward, do the same with the second binoculars, and after some time, the zombie will shoot two lasers into the sky, and music will start playing.

Afterward, turn towards the bus and wait until the zombies get on it and start dancing!