The fantastic story about the vast fish that becomes a vast bird and flies from the Northern Darkness to the Southern Darkness which opens the Zhuangzi has never much appealed to me. This may be in part due to a desire that things be "true"; I fear that Zhuangzi believed in such mythology. However, when one considers that he probably made it up out of whole cloth and that when he cites it as contained within an "authoritative" book, the Universal Joke Book of Tall Tales, which he also made up, things start to take a different turn. The Zhuangzi, it turns out, is that joke book.
But all this is largely conjectural, one possible interpretation among many others equally as possible. Kuang-Ming Wu (The Butterfly as Companion) brings a basket of such possibilities to our attention and thereby demonstrates how we might enter into the joke and come away with our own laughter; if to laugh is the point, and in some sense the only point in life is to laugh, then what difference would the supposed truth of the story or the true interpretation make? "The truth of the world accommodates many lies to be understood," writes Wu. "This is the enrichment of life, that truth requires lies."
Wu suggests that it has the attributes of a creation myth with that special Chinese sensibility for the interplay of Yin and Yang. In the Northern Darkness (Yin; dao that cannot be dao-ed) lives a vast fish whose name means "roe', the mere suggestion of a fish — a fish that “has not yet begun to be”. The fish transforms into a vast bird who is compelled to fly a vast distance, using the "six-month breath of Heaven" (the monsoon winds), to the Southern Darkness, the Heavenly Pool, the embodiment of Nature, Yang; the dao that can be dao-ed. The Yin-Fish in the Yin-Darkness transforms into a Yang-Bird that seeks the Yang-Darkness; will it there re-transform into a Yin-Fish?
The story begins and ends in Darkness, from Mystery to mystery, echoing the first chapter of the Laozi; nothing is explained. Always and ever all is Mystery. We emerge from Darkness, we return to Darkness. Are we not also that Darkness? "Who can see his head as Nothingness, his spine as life, and his ass as death? He will be my friend!" Who can be not only her individuated life experience, but also the encompassing Mystery? She shall be the friend of the cosmos. She will be at home wherever she is — or is not.
You can check out Scott's writings on Zhuangzi here.