At the end of the Heart Sutra we chant Gya tei Gya tei…. – which means together we go beyond, across the river, to the far Shore. The far shore in this context means Nirvana.
What we need to understand is that zazen is the entire ground; this shore, the far shore, the ground beneath the river.
Therefore do not stagnate in emptiness. Wear neither the mask of the self nor the mask of false equanimity. Just allow everything to flood through you, like light.