PRETORIA, South Africa — Jacob Zuma became president of Africa's economic powerhouse Saturday, vowing to work to fulfill the dreams of all South Africans after he overcame corruption and sex scandals to reach the nation's highest office. Tens of thousands of spectators at Zuma's inauguration screamed their approval, dignitaries applauded and a Zulu praise singer in traditional animal skins extolled the virtues of Zuma, whose popularity rivals only that of Nelson Mandela. "The dreams and hopes of all the people of our country must be fulfilled," Zuma promised.