Easter Egg can be done solo but recommend 2-4 to make one step easier

Due to not seeing anyone getting close to completing, because it being appently being too diffuclt or something here's the full Main Quest guide

Main Quest:

Step 1: Craft and turn on power
 Open the shed for 1000 Points
 Find and pick up the Panel
 Open the Shop for 1250 Points
 Find and pick up the Power Switch
 Return to the shed and craft the Power
 Turn on Power

Step 2: Acquire key card
 In the fire pit next to the crashed bus, there is a zombie hand holding a
key card near the back of the bus on the edge of the fire.
 Pick up the Key Card and use it to open the Lab above the Store

Step 3: Link Teleport to the master Switch
 Open to the Teleporter for 2000 Points
 Go up to the Teleporter and press to activate link
 If haven’t already use the Key Card to open to the Lab above the Store
 Go up to the master switch and press to Link to mainframe
 Return to the teleporter to teleport for 1000 Points


Step 4: Radios
 There are 3 radios on the map, that need to be activated in Order
 The first radio is in spawn on one of the seats.
 The Second radio is in the power shed opposite to the Double Tap Machine.
 The 3rd radio is in the lab, onto of a console next to the teleporter return pad.
 9 Soul pods will then spawn around the map.

Step 5: Build the bomb
 6 parts hidden around the map

Step 6: Complete the soul collection
 (locations 1-7 can be done before step 1)
 There are 9 soul pods that need to be filled
 Location 1: Spawn, next to box location
 Location 2: Under bus shelter opposite the shop
 Location 3: with the cars opposite the power shed
 Location 4: next to stamina up
 Location 5: near the jug machine
 Location 6: Inside of the power shed
 Location 7: behind the counter in the shop
 Location 8: In the lab next to the wonder fizz machine (Step 2 is required)
 Location 9: Opposite the male kick machine (Step 5 is required)

Step 7: BOSS FIGHT and buyable ending
 This fight is completed in Three stages
 Activating the console will trigger all the zombies in the round will despawn and no more
zombies will spawn until the end of stage 1
 An audio message will play telling the player to press the first switch opposite the main
console
 Once switch one is pressed, infinite dogs will spawn. The Player must survive for two
minutes
 At the end of the time the dogs will stop spawning and an audio message will play
 Zombies start spawning again, and there is a 2-minute cool down between stages
 Pressing switch two will again kill off the zombies and spawn infinite dogs this time the
player must survive 5 minutes.
 Again, the zombies will spawn after this stage and the player must wait 2 mins to cool
down
 The third and final button will be ready, the player will now need to survive 8 minutes from
infinite dog spawns, however after 6 minutes zombies will start spawning as well.
 After this time an audio message will play, and a door will open allowing the player to buy
a portal to end the game

Enjoy :/