It is pronounced "ZAKKU". (Consonants are pronounced more or less the same way as in English. "A" sounds like a in father, but shorter. "U" sounds like oo in hook, but with less rounding of the lips.)
Zachary
It is pronounced "ZAKARII". (Consonants are pronounced more or less the same way as in English. "A" sounds like a in father, but shorter. "I" sounds like ee in meet, but shorter. Double vowels like "II" are held for twice the duration of single vowels.)
Chinese
Name : Zachary
Chinese characters : 扎卡里
Pinyin : Zā kǎ lǐ