Zen philosophy is a part Buddhism. Buddha's follower, Mahakshyap's disciple, Bodhidharma, went to China to spread Buddhism. However, the Tao philosophy was already prevalent in China. So, the Zen philosophy is a mix of Taoism and Buddhism. Zen philosophy believes that the world is perfect the way it is, and we don't need to change it. We should be grateful and compassionate, and lead life playfully.
Zen philosophy is about living in the present moment, to be an observer, and not to bring any thoughts or judgments in the mind about what is being observed. Its say only observe and hear, without bringing in any emotion or thoughts. It does not follow any rituals, doctrines, or principles. The Master has only one aim - to bring the student in state of thoughtlessness, and to live in the present moment only. For this the Master uses various techniques, including making the student do arduous work, shouting at him, ignoring him, etc. The student needs to find the answers to his questions within himself only. The Master does not provide the answers, he only explains that in a state of thoughtlessness or meditation the student will get the answers.
Zen Haikus are the shortest poetries in the world, that may seem very abstract, but are the most beautiful poems, that paint the picture of the present moment that is observed by the Zen Master.