zany

silly

Example:

Jim is the zany one in the end office. He always wears bright yellow shirts.

zapped

very tired

Example:

I'm going home. It's ten 'o' clock and I'm zapped.

zero

a person who is not noticed

Example:

Him? He's the zero who works in the mail room. Don't even know his name.

zilch

nothing

Example:

He knows zilch about anything.

zip

nothing

Example:

Alan knows zip about the problem. He didn't work on the project.