The Heart Sutra begins:
The Bodhisattva of Compassion, practicing the highest wisdom, realises the five skandas are empty, and thereby relieves all suffering.
In other words:
The Bodhisattva of Compassion, practicing zazen, makes real the emptiness of all experience, and so relieves all suffering
The passage is a mythical way of talking about practice. When we practice, we are practicing not from the position of self, but from the position of Buddha, Kanzeon. We are not cultivating compassionate awareness, we are compassionate awareness. Practice is the palace of Enlightenment, not the door.
Emptiness is the release of all things into their infinite, ungraspable nature.