ず[に] ... (attendant circumstances, means)
文法の解説は英語です。
用法
Vないform ~~ない~~ + ず[に]... Indicates attendant circumstances or means. It is the same as ないで but is more in the written than in the spoken style.
例文
その男は先週の土曜日にこの店に来て、一言も話さず、酒を飲んでいた。
That guy came to this bar last Saturday and was drinking without saying a word.