How do you use the Four Great Vows in Zen practice?

The Four Great Vows, sometimes referred to as the Four Bodhisattva Vows, are used both in the Mahayana Buddhist tradition and in Zen. A “Bodhisattva” is someone who dedicates their lives to helping others. Instead of relieving our own suffering, we also help others when they are suffering. We use the Four Great Vows to help set the intention of this Bodhisattva spirit. There are many versions of them; here is one translation used in the Kwan Um School:

Sentient beings are numberless. We vow to save them all.
Delusions are endless. We vow to cut through them all.
The teachings are infinite. We vow to learn them all.
The Buddha Way is inconceivable. We vow to attain it.

I teach the first vow giving direction to our practice. Why do we practice Zen? We vow to use our practice to help other people, creatures, and the environment. The second vow states delusions are endless. This means that our views, opinions, judgments, and likes and dislikes are constant, and can easily get in the way of clearly perceiving what is in front of us in this moment. We vow to cut the string of attachment to these things so we can see the moment with openness and clarity. The third great vow is seeing everything in our lives as a teaching. The sound of a dog barking, the person who is angry at us, the smell of a flower. All of this teaching is pointing to our true self, our enlightened nature. Clearly seeing these teachings helps us to develop wisdom. The last vow is that the Buddha way is inconceivable, meaning our enlightened nature cannot be understood merely by our understanding. It can only be understood by attaining it.

From the book No-Nonsense Zen for Beginners