In standard Vietnamese (aka the textbook version), "gi" sounds like the "z" in the English word "zero" while "d" sounds like "y" in "you". However, as dialects play a very important role in spoken Vietnamese, these are pronounced differently in different regions. In the Northern dialect (relatively close to the standard textbook language), both "d" and "gi" (and also "r") are pronounced like "z" in "zero". In the Southern dialect, both "d" and "gi" are pronounced like "y" in "you". Central Vietnam has many local dialects (Thanh Hoa, Nghe An, Hue, Quang Nam, etc.), where the pronunciations more or less range between the Northern and Southern versions.