The mighty bird Peng overflies the tiny quail, dove and cicada, who look up and laugh at such a grandiose, yet to their thinking useless, exhibition of the possibilities of flight. Ziporyn observes that this may very well be Zhuangzi's opening swipe at his good friend and sparring partner Huizi (Ironies of Oneness and Difference, p. 163, note 32). Peng is to his scoffers as Zhuangzi is to Huizi.
In many respects, there is good reason to believe that Zhuangzi wrote for and in answer to Huizi. His arguments are often a continuation of those of Huizi, though they lead him to altogether different conclusions in terms of how one might best respond to the human experience. His frequent use of Huizi as a foil to make his points provides further evidence to this effect.
With this in mind, the closing two vignettes of the introductory chapter that begins with the flight of Peng take on a new depth of personal significance. In both, Huizi suggests that Zhuangzi's ideas are "big, but useless". Zhuangzi replies that Huizi has clearly failed to realize the usefulness of the useless (just as Peng's scoffers have failed to appreciate the value of living in awareness of one's transience and embedding in Oblivion).
There is also the (probably apocryphal) story (in the 17th chapter) of Zhuangzi's visit to Liang where Huizi was prime minister. Thinking that Zhuangzi was intending to take his position, Huizi tries unsuccessfully to intercept him, but Zhuangzi shows up quite voluntarily and scathingly likens Huizi's concern to that of an owl clinging fearfully to a rotten rat as a vast and majestic bird who, like Peng, arises from the Northern Sea and flies to the Southern Sea, and only eats the extremely rare fruit of the bamboo, flies overhead.
This personal and somewhat autobiographical dimension helps to further illuminate the context and meaning of some of Zhuangzi's ideas. However, there are also lessons to be learned in the simple fact that Zhuangzi's philosophy was a very personal and subjective one. This is not science. This is a self working through for itself a liberating response to life, and in its overt subjectivity, essentially suggesting we do the same.
There are those, of course, who most scholar-fully and seriously, will assure us that Zhuangzi’s authorship of the Inner Chapters is highly doubtful, and therefore . . . what? I reply that it is also highly unlikely that a bird named Peng transforms from a fish, ascends ninety thousand miles, and flies to a Southern Oblivion. So what? The harmful myths are the ones not recognized as such, and in our age these tend to be the ones that lurk behind the facades of so-called objectivity. They, too, fail to understand the usefulness of the useless. The point is to awaken to the dreaming, not from it. And this was the objective of whoever wrote this particular myth.
You can check out Scott's writings on Zhuangzi here.