Green’s Dictionary of Slang

z n.2

also zee
[abbr. oz.]
(US drugs)

1. 1oz (28g) of cannabis.

[US]R.A. Spears Sl. and Jargon of Drugs and Drink.

2. 1oz (28g) of heroin or crack cocaine.

[US]Wentworth & Flexner DAS.
[US]H. Gould Fort Apache, The Bronx 267: You got nine ounces out of that little old zee I sold you.
[US]ONDCP Street Terms 23: Z — 1 ounce of heroin.
J. Spades ‘Flexin’’ [lyrics] Sell bricks or you sell zizz then the pagans them / A go tell feds.
67 ‘Dead Up’ [lyrics] Walk around with 5 zeds in my pouch.
1011 ‘No Hook’ [lyrics] I just put 4 z’s in pebs, plus I get bits for man if they need it.