The use of paradox in Zen teaching is quite a normal way to do. It is to cut or destroy the normal intellect thinking. The question who a man really is can´t explained by words. The answer can be found only with the experience of intuitive knowledge. With help of paradoxes disciple can get leaded to the right path. A Zen master leads his followers and students into the truth. Sometime it is done by a single phrase who intuitive designed to destroy the student particular of so called demon of ignorance.
For those who discovered the nature of Reality, there is nothing old or new, concepts become meaningless and reason leads to error.
In Zen or Chan in Chinese therm there is the concept of sudden and complete enlightenment. It is possible here and now if you are able to release. To get it t is necessary to rise above such relative concepts as good and evil, sought and found,enlightened and unenlightened and all the rest of these kind of paradigm. In daoist therms it is be explained like before Yin Yang shows up or be one or also Wuji. Intuitive realization of the unity or of the Absolute means there is nothing to be attained, one does not enter Nirvana. Intuitive realization of oneness is like to enter the Nirvana there no other place to go or to enter. The one who have actually achieved these level are knowing about the impossibility of communicating it in words.