Not to be outdone by those Greeks, the USA apparently has 14 pronunciations.

Been an uneducated Brit, whose previous experience with the word was limited to describing part of a helicopter, I used to pronounce it GaIro. My wife corrected that to dZaIro, but since her upbringing was somewhat cosmopolitan, what does she know?

http://linguistlist.org/issues/6/6-1641.html gives the Boston pronunciation as yiro.