It'd seem that there are zen/buddhist practices and elements in Fight Club:
- Narrator does bunches of haikus
- Narrator's home intends to be zen-like looking
- Penguin says slide
- Car crash scene Tyler says Stop trying to control everything and just let go!
- Detachment is a major theme since first conversation between Narrator-Tyler
- Project Mayhem candidates are requested to have a minimal amount of possesions
- Buddhist aspect of Project Mayhem? Searching for truth. 4th rule: No lies.
- And Tyler even quotes a buddhist idea regarding the selection of candidates.
Excerpt from Book, Chapter 17 (= the movie). This is how Buddhist temples have tested applicants going back for bahzillion years, Tyler says. You tell the applicant to go away, and if his resolve is so strong that he waits at the entrance without food or shelter or encouragement for three days, then and only then can he enter and begin the training.