Green’s Dictionary of Slang

zol n.

also zoll
[ety. unknown; zol is recorded as 1950s US/Mex. border drug use, but no provable link exists; Branford, Dict. of South African English (4th edn, 1993) notes the obs. trade name of miniature cheroots but gives no date; if it precedes drug use it would be an obvious root]
[1940s+] (S.Afr. drugs)

1. a hand-rolled cigarette.

2. a marijuana cigarette.

3. a measure of marijuana, enough to make a single cigarette.

4. cannabis; also attrib.

In compounds

zol monkey (n.)

a habitual smoker of cannabis.

zol rooker (n.)

a marijuana smoker.