If the z is the letter that looks like an upsidedown pi with a little tail in the lower right hand corner we usually transliterate it as ts in English. This would be the letter that is doubled in the Russian word for pizza and the initial letter in the word we normally transliterate as Tsar. The one we transliterate as z in English is the one that looks like the numeral 3 and is the first letter in 3gpaBcmByume = zdravstvuite. Other languages may use other transliteration schemes.