Standing alone and unchanging,
One can observe every mystery,
Present at every moment and ceaselessly continuing -
This is the gateway to indescribable marvels.
Lao Tzu - Dao De Ching
Zhan zhuang is to be still like a tree and grounded. When our external is still, we can look within and feel the process(es) that's occurring within. We are in constant motion and each time you have a chance to discover and experience more.