I know someone called Xzavier, and his name is indeed pronounced ex-ZAY-vee-ur. Apparently the parents weren't sure whether Xavier was pronounced ZAY-vee-ur or ex-AY-vee-ur, so they included both pronunciations to keep everyone happy.(I actually didn't know anyone else had this name! I thought it was a one-off oddity. An important lesson for anyone trying to be unique I guess).