In brief… made in 1963, "Ganga Zumba" wasn’t released until 1972 because there was a military coup in Brazil in 1963, and films about revolutions, even those taking place in the 17th century, were considered politically dangerous. 

From the beginning of European involvement, until today, there have been innumerable slave and peasant revolts. Usually they were short-lived, brutally suppressed affairs. 
This *forgotten* film recounts the story of one such revolt, in 1641, in which the slaves formed their own nation (or "quilombo") and ran it for over 50 years. 
The film was directed by Brazilian filmmaker Carlos Diegues, who, by the way, also directed the more well-known "Quilombo," 20 years after he made "Ganga Zumba" – which is essentially an updated rendition of "Ganga." And some of the starring actors from "Ganga," also starred in "Quilombo."
If you’ve never seen this film, as it doesn’t seem to exist on DVD or VHS format, you’re in luck, because I found the entire thing on YouTube, however, none of is subtitled, so unless you understand Portuguese, you’ll struggle watching it. However, as it’s a film with not a lot of dialogue, you won’t necessarily miss a lot. Besides, even in those instances where there is conversation, as long you’re paying attention, the images alone are often enough to understand the story as it unfolds.
Hopefully, whoever owns the rights to it will decide to reintroduce it to the world, restored and subtitled for commercial distribution.
In the meantime, here’s the full non-subtitled film from YouTube: