The Fiqh books say that you cannot, but this opinion is not true. Because one of the eight groups that can receive Zakat is called Muallafatul Quloob; meaning those, whose hearts to be warmed to Islam (See Surah At-Tawbah, Verse: 60). It is obvious that these people would not be Muslims. In fact, all of the other seven groups also do not have a condition to be Muslims. It is clear from the verses and hadiths that non-Muslims can receive Zakat. But of course, giving Zakat to Muslims is preferred.