Ziqi's metaphor of the wind in the trees ends in asking who is the blower. Who (or what) makes all this happen? He concludes with the obvious observation that we do not know. All that we are then left with is the question: Who?
Ziporyn comments: "This 'who', in my opinion, is a gloss on 'I lost me'. [Losing one's 'me' is the discovery of one's unanswerable who?-ness.] This question word is Zhuangzi's typical yes/no [he always ends in a question, not an answer], the same yes/no we saw implied in the structure of 'I' lost 'me', the simultaneous presence and absence of the self [If the "me" is lost, who is the "I"? To be "empty", to realize "no-self", is not to have no self, but to have a self of a different awareness.], and Zhuangzi's insistence on ending all his discussions with a wavering pair of questions, rather than a conclusion. The blower, then, is the self, always present and absent in the sounds. The true self, in short, is 'Who?' Or, to put it otherwise, the true self is 'Is there really a true self or not?'" (The bracketed comments are my own.)
Again: "[T]he Dao is to the world as the self is to the passing emotional experiences. [Zhuangzi has identified these expressions of personality as equivalent to the sounds issuing from the trees.] It is both present and absent — in other words 'I' have lost 'me'."
Finally: "To be both sides means to be the eternal Who? that blows these different transforming pipings forth — not to be any someone always, for that would be one of the different tones piped forth, but not to be no one either, for that would mean no piping. Rather to be Who? . . . a ceaseless question mark . . . ."
We ask Who? makes all this happen. We, too, are Who? To lose one's 'me' is to lose one's sense of being a fixed identity; there is identity, but it is, like knowing, "peculiarly unfixed". To realize this is to be released into vastness so that one can say, "I and the ten thousand things are one", not as truth, but as truthfully experienced.
You can check out Scott's writings on Zhuangzi here.