z, v. — Green’s Dictionary of Slang

z v.

also ze, z-out, z’s, zzz

(US black/teen) to sleep.

1967–8		Baker et al. CUSS.
1968		D. O’Grady A Bottle of Sandwiches 131: Ernie was still zzzzing away.
1972		D. Claerbaut Black Jargon in White America 87: z’sing v. sleeping; napping.
1981		Eble Campus Sl. Mar. 7: z-out – to fall asleep.
1996		Eble Sl. and Sociability 30: In college slang out is the most productive particle: [...] z-out ‘go to sleep.’.

z’d out (adj.)

(US teen) unable to wake up properly, still sleepy.

1986		F. Pfeil Goodman 2020 90: Anna went once, must have been three hundred people in the room, half of them z’d out beyond hearing.
2006		J.L. Marshall Flashlight Dream 193: You’re Z’d out, never to return.