How were "organized human beings" able to defeat "organized modern technology" in Chapter 18 of A People's History of the United States?
What Zinn is talking about here is the ability of the North Vietnamese and the Vietcong (the organized human beings) to defeat the US military (the organized modern technology). Zinn argues that this was possible basically because the communists were popular among the people and the US-backed government was not.
Zinn argues that Ho Chi Minh and the communists had the backing of the majority of the people of Vietnam. He goes on to point out that the Diem government and those that followed it had very little support among the people. All they had, Zinn says, was the support of US military technology.
Zinn, then, is painting this war as a victory of people fighting for an idea they believed in over what he sees as an oppressive military using its technology to try to make up for the fact that the cause it was supporting completely lacked legitimacy and popular support.