Final answer:
The rejection of British government's plans for majority rule in Rhodesia and the white leadership's declaration of independence sparked Zimbabwean nationalism among the black middle and working class.
Step-by-step explanation:
Black Zimbabwean nationalism among the middle and working class was ultimately sparked by the rejection of British government's plans for majority rule in Rhodesia, which led to a declaration of independence by the white leadership in 1965.
This declaration was not recognized by Britain, and the United Nations imposed sanctions against the white leadership. In response, black Africans initiated an internal guerrilla uprising to fight for free elections that would include them.
Finally, in 1980, independence was granted and the country's name was officially changed from Rhodesia to Zimbabwe.