The Truth is realized in an instant; the Act is practiced step by step.
When reading, only read. When eating, only eat. When thinking, only think.
The practice of Zen never explains anything. Zen simply points directly at our mind, our true self, so that we can directly attain enlightenment and help all beings.
This is the whole point of the Heart Sutra. From moment to moment, when you are doing something, just do.
Zen means putting it all down, cutting off all thinking, and returning to your pure and clear original nature.