The Romanians got the instrument from the Turks, who got it from the Persians or the Arabs. Who got it from the Egyptians or the Sumerians.

Zamfir was a student of Tiberiu Alexandru, and the standard text on the Romanian style is by Alexandru. I think it's humungous and out of print and I've never seen one. (Alexandru's book on Romanian folk music is wonderful - Bert Lloyd got it translated into English)

The African-American tradition has roots that must have diverged from the Romanian/Turkish/Persian/Arabic one during the time of the Roman Empire or even earlier. So they didn't have a lot to learn from Zamfir.