There are different zombie types to encounter. Use whatever means you can to get by them and find the artifact to complete the mission. Zombie Types are:-Walker (Normal walking or running zombie)-Crawler(Crawls on all fours and is faster than walkers)-Brawler(Faster than walkers and has more health and does more damage)-Rage(Gives player radiation when close and enrages nearby zombies)-Novalight(Shoots projectiles)-Boomer(Explodes when killed)-Elite(Has energy shields, sprints, and does the most damage)Zombies can only be killed by headshots. Except for one variant, the Novalight