I am only half-way through the book Skepticism, Relativism, and Ethics in the Zhuangzi and though admittedly my mind begins to cloud over when exposed to all the nuances and distinctions possible with respect to these weighty philosophical issues, still I find it thought-provoking and would certainly recommend it. However, before my mind becomes too clouded, and more importantly, before I can no longer support the myth that my ideas are my own, I'd like to weigh-in with my own understanding of Zhuangzi's skepticism.
Perhaps the best place to start is with the observation that Zhuangzi probably wouldn't have a clue what all this discussion about 'skepticism' has to do with anything. I'd like to understand Zhuangzi, not how his skepticism fits into two millennia of subsequent philosophizing. In the end, he is interested in the limits of reason only because, in the discovery of those limits, we are presented with the possibility of going beyond them. He is not interested in epistemology or a theory of knowledge; he is interested in freedom. All his word games and his mischievous use of the arguments of his more rationalist contemporaries are intended to bring us to the boundaries beyond which reason cannot go. Would he not be amazed to find us trying to reconstruct his fish-trap so as to understand his message?
Zhuangzi's position on reason seems clear enough: It's great within the context of its usefulness — just like morality. But reason clearly cannot provide us with the unmovable foundation we seem to require; it is "peculiarly unfixed". Thus he says, Reason has perfected itself when it discovers its limits. This reason alone suffices to honor reason.
What follows is not a new and this time sure foundation that relies on something other than reason (an 'enlightenment' where "all is made clear", for instance); no, every species of surety has fallen away with reason itself. Rather, it is an abandonment into the emptiness (contentlessness) of not-knowing. It is not not-knowing. It is release into a life whose most fundamental given is its unfixed transience. It is the freedom that obtains from relying on nothing.
Nature has no Reason. Reason can discover infinite reasons within nature, but it cannot discover a reason for Nature. When did it ever need one? When one species of animal evolved self-conscious awareness. Is this a "sixth finger", a useless appendage? Not at all; it has led to the amazing and unparalleled success of this animal. But in the end, it might also prove to be too much of a good thing. Lemmings apparently know this possibility; when they have become so successful at breeding that they are about to eat themselves out of house and home, they (mythically?) make a mass exodus to the waiting sea. That's why there are still lemmings.
You can check out Scott's writings on Zhuangzi here.