Minimum RAM Allocation:

• SinglePlayer: 4GB
• Client: 4GB
• Server: 4GB

Recommended RAM Allocation:

• SinglePlayer: 5GB ~ 6GB
• Client: 5GB ~ 6GB
• Server: 5GB ~ 6GB
  
  

For Single Player, please go to More World Options when you're creating a new world, and click Cities button on the top right, change the profile to Everywhere.

Please use the latest version to ensure the best experience as they have bug fixes.

Note: If you're are hosting server through online websites, make sure the Enable Command Blocks setting is enabled, otherwise you might miss some of the vehicle spawns and more.

Embeddium is already within the modpack. Complementary/Reimagined Shader or any other shader is HIGHLY recommended for the visuals if you have the hardware for it.

This Modpack Is Highly Inspired By : 

DeceasedCraft - Modern Zombie Apocalypse

Play It Here: https://www.curseforge.com/minecraft/modpacks/deceasedcraft