The Heart Sutra is the distillation of the vast Prajñāpāramitā sutras.
The version we chant divides into 2: an initial statement, then a long monologue by Avalokiteśvara, the Bodhisattva of Compassion.
The initial statement is:
The bodhisattva of compassion, practising Zazen actualises the emptiness of the five skandas and thus relieves all suffering.
This is a mythical rendering of our experience as we sit. The critical thing is that it isn’t a person sitting, and that emptiness is something felt, not a statement about the nature of reality Thus, we can say that emptiness, compassion, no-self and suffering relieved are all facets of Zazen.
This is a very different practice from one concerned with gain, or change.