The noun zayn is not in the Quran, but its root is: “Allah has endeared faith to you and made it beautiful (zayyanahu) in your hearts” (49:7); “Wealth and children are the adornment (zina) of worldly life” (18:46). The Prophet ﷺ said: “Beautify the Quran with your voices” (Abu Dawud 1468).
Meaning of the name Zain
Zayn is the opposite of shayn, “ugliness”: beauty, grace, what adorns and embellishes (root z-y-n, that of zina, “adornment”). The name is given alone, unisex in the Middle East, or in compounds: Zayn al-ʿAbidin, “adornment of the worshippers”, the epithet of ʿAli ibn al-Husayn, great-grandson of the Prophet ﷺ.
And know that among you is the Messenger of Allāh. If he were to obey you in much of the matter, you would be in difficulty, but Allāh has endeared to you the faith and has made it pleasing in your hearts and has made hateful to you disbelief, defiance and disobedience. Those are the [rightly] guided.
Wealth and children are [but] adornment of the worldly life. But the enduring good deeds are better to your Lord for reward and better for [one's] hope.