I read Zen and the Art of Motorcycle Maintenance by Robert M. Pirsig a few years ago and really enjoyed it. However I'm not convinced it's got anything to do with Zen. From what I remember the protagonist spends a lot of time fixing his motorbike and contemplating the notion of quality. But does the text link into Buddhism generally and Zen specifically? If not, why has it got Zen in the title?
The main idea is pretty Zen yes. The premise of the book is that Western philosophy made a wrong turn at Aristotle, who placed (conceptual) Truth at the top of the hierarchy of all knowable, thereby subsuming the Good (aka Quality aka Beauty) as a byproduct of Truth. Through this sleight of hands the conceptual has falsely acquired status of universal, while the experiential from being the mother of conceptual became its slave and hostage. Instead, argues the author, the (preconceptual) Good exists in the sphere of direct experience, and can be known directly. According to author, true understanding of Quality, Beauty and Ethics is possible only through such direct nonconceptual contact with the principle of Good. At which point Good is reinstated to the throne of knowable and Truth becomes merely one of alternative ways of attaining Good.
This very much parallels Zen Buddhism's interpretation of Buddha-Dharma, according to which Self-Existing Enlightenment is not to be understood through analytical reasoning, but is awakened to through direct experience. Meditation, koan work, interviews with Zen Master, calligraphy, tea ceremony etc. are all means of getting in touch with this direct experience, which in Zen Buddhism is emphasized over analytical study of texts.
In my opinion it would not be too much of a stretch to equate book author's direct insight into Good/Quality with Enlightenment as it is understood in Zen Buddhism. Although technically, Zen Buddhism goes further in that it gets one into direct contact not just with Good, but also with the very Emptiness itself. So strictly speaking the author falls short of full-scale Enlightenment, but still does a good job illuminating the trap of strict rationality and the primacy of direct experience.
I think the answer is not much. Robert Pirsig states that
it should in no way be associated with that great body of factual information relating to orthodox Zen Buddhist practice. It's not very factual on motorcycles, either.
The title itself is apparently a play on the book Zen and the Art of Archery
However to say it isn't about Zen doesn't mean it's nothing to do with the enlightenment experience. The guys over at Partially Examined life when discussing don't talk about Zen but do talk about enlightenment. In the pivotal point of the book the protagonist undergoes a physiological break. Pirsig himself refused to say whether the experience was a physiological/psychotic break or a genuine enlightment experience
The word Zen is derived from Pali word Jhāna which means concentrated or absorbed state of mind. So whenever I see the word Zen outside of Religious work I assume it just refered to absorption . Therefore I would assume in your case it would refer to absorption into art of motorcycle repairing :).