On the more common layout of the Tree of Life, Zayin connects Chokmah, Wisdom, to Tipherah, Beauty. In the Ari's version, it connects Chokmah to Geburah, Judgement. In either arrangement, Zayin is Wisdom coming down to the world below. It is an active step of introducing Wisdom into the decisions that need to be made. Judgement without Wisdom will lack Mercy. Beauty without Wisdom doesn't change the heart. Zayin also means seven. Seven represents the seventh day of creation, when the work had been accomplished. It represents the seven days of the week. It represents the seven visible lights in the solar system, the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. Seven is the number of completion.
On the Western Tree, Zayin connects Binah, Understanding, to Tipherah, bringing down the other side of the Supernal Triad than what the Hebrew Tree brings down. Both Wisdom and Understanding are necessary for Beauty to fully have the impact it needs to. In Zayin, the Lovers wait, but after the Fool has tramped by, the Chariot arrives here.
The Lovers in Zayin are a direct symbol of the Wife crowning the Husband. In Vev, the Lovers come together, but in Zayin, they are married. Zayin is the completion of relationships, and represents each partner taking an active role in that relationship. Their Desire is for each other, and they Will to keep it that way. The Lovers are also the Bride and the Bridegroom, G-d and Shekhinah, the Non-Existent and the Divine Mirror.
And then the Fool comes. In Zayin, he finds his Strength. Not the Strength of Aleph, which helped him start on the road, but the Strength of Zayin, which will help him complete his journey.
After the Fool has moved on, we find the Chariot in Zayin. The Chariot is the union of opposites, the dualities in unison. We see that here, for Zayin is both the strong arm in battle that the Chariot takes with it, and the triumphant return after the battle is complete. The Chariot is always in motion, always spinning like the Divine Chariot in Ezekiel's vision. This is the active role of Zayin.
Zayin is about being active. Are you taking an active role in the world around you or just sitting back and watching? What choices and opportunities are before you? It is time to choose and do it, time to stop putting the decision off. What is your Desire? What is your Will? If you don't pursue them, what's the point of desiring, what's the point of will? Go out and seek your true Desire, not your wants and needs. These are temporary, but true Desire and true Will are enduring. It is time, in this moment, in the Now, in the Silence and the Stillness, to bring it to completion.