In the famous Uji chapter of Shobogenzo, The good old Dogen writes the following:

(...)Since we human beings are continually arranging the bits and pieces of what we experience in order to fashion ‘a whole universe’, we must take care to look upon this welter of living beings and physical objects as ‘sometime’ things… In a similar manner, we are continually arranging bits and pieces of what we experience in order to fashion them into what we call ‘a self ’, which we treat as ‘myself ’: this is the same as the principle of ‘we ourselves are just for a time’(...).
It is not hard to see how much we are the maker of this, the very origin of the dramatic-operadic show. We are busy weaving the very few threads of reality we can get hold of into a piece of complete fictious nature. And in the process, we completely miss the point, turning sentient and insentient beings into objects. The big subject, the"I", this is "me", "my thoughts" "myself" is being manufactured in the meantime, getting a sense and evidence of its own existence as an aggressive or seductive relationship with the so called world is taking place ( "I" have to win, conquer, possess, you have to love me, hear me, look at me...).

It is not difficult to understand that this is yet another version of our body and the bodies of others fall away, a deconstructing task, or, to be more precise, a supreme action, empty of any agendas and purposes, that strip the whole thing body-mind-universe and get to the bare bones and marrow. To undo the fiction of the self is our job, not to undo the self itself ( as there is no self or ego from the very beginning).

Zazen is the gate and space where this game of ego-lego is seen for what it is.