英语单词'zoo'以字母z开头。

The word 'zoo' begins with the letter ___z.

他太累了，一躺下就开始打呼噜。

He was exhausted and began snoring ___zzz as soon as he lay down.

在这个代数问题中，我们需要求出z的值。

In this algebra problem, we need to find the value of ___z.