The Fiqh books say that you cannot, but this opinion is not true. Because one of the eight groups of people who can receive Zakat is called “Muallafatul Quloob”; meaning “those, whose hearts to be warmed to Islam”, according to Surah At-Tawbah, Verse: 60. It is obvious that these people would not be Muslims. Indeed, none of the people in other seven groups have to be Muslims, either. It is clear from the verses and hadiths that non-Muslims can receive Zakat. But of course, giving Zakat to Muslims is preferred.