Sam, who was using the concealment technique right now, killed the Zombies that were in front of him. Well, you can say that at least 20 zombies were in front of him. He did not want to waste anymore and because of this, he just killed them as fast as he could, using his energy mode. Sam still was not able to use the energy mode while also using the spirit technique. He was still working on that besides his other technique, but that will need him much time to master. As you know, the fastest way for him to kill those monsters was by using his energy mode while using his fast-cut technique.