I finally worked out why the translation that I'm doing has a so little similarity with the drama version. There are in total three novels by this author that are entitled The Evil Hypnotist 1 - 2 and 3.
The screenwriters have taken elements from all three of them and mixed them together in their script.
The detective Luo Fei is the protagonist in all three volumes.
The "zombie" case is from the 1st volume, where Ling Mingding is the hypnotist helping Luo Fei. He disappears at the end of the 1st volume.
Most of the cases that we see in the drama (based on the theme of the seven mortal sins and inspired by the film Se7en) come from the 2nd volume. Here Xiao XiFeng is the hypnotist working with Luo Fei.
Lu FengPing only makes an appearance in the 3rd volume which also has the case of the girls from the orphanage.