Can non-Muslims drink Zam-Zam? Please reply as soon as possible.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

There is no objection to give Zam Zam water to a non-Muslim and let him drink it as there is no evidence contradicting that.

In fact, the Prophet (Sallallahu Alaihi wa Sallam) spent two years after conquering Makkah, leaving the door of the Haram Mosque open for non-Muslims to perform Hajj and Umrah and it is not reported that he ever prevented them from drinking Zam Zam water.  We remind you that the most important thing, when calling non-Muslims, is to convince them of monotheism.  "The Prophet (Sallallahu Alaihi wa Sallam) said to Muaz when he sent him to Yemen to call them to Islam: 'The first thing to invite them to perform is the Shahadha: testimony that there's no deity worth worshipping except Allah and that Muhammad is His Messenger…" [Al-Bukhari and Muslim]

Allah knows best.