Top-seeded Zhang, who won the doubles gold with Wang Nan on Friday, demolished North Korean Kim Hyang-mi 4-0 in just 26 minutes to keep China on track to sweep all four table tennis golds for the third straight Olympics.
"Winning exacts a high price physically and mentally. It was a mental battle with myself," said Zhang, pegged to be the next team leader of the dominant Chinese table tennis team.
Teng Haibin maintained a perfect bodyline in the men's pommel horse to hand China their first gymnastics gold medal of the Athens Games.
"I'm very excited, it was very important for us to win today," said Teng.
In a victory that meant a first Olympic medal in tennis for China, Li Ting and Sun Tian Tian won the women's doubles gold with a 6-3, 6-3 defeat of Spain's Conchita Martinez and Virginia Ruano Pascual.
Earlier, Chinese shooter Jia Zhanbo harvested a gold medal men's 50-metre rife three-position target event after American Matthew Emmons fired at the wrong target as he neared victory.
China led the medals table on Sunday evening with 22 golds, 14 silvers and 10 bronzes -- one gold above the Americans and closing in on their record of 24 golds, won at Sydney.
Japan, holding onto an unexpected third place in the medals table, burnished their most golden Games in three decades with a gutsy run by Mizuki Noguchi to win the women's marathon title.
Noguchi, the world silver medallist, produced a killer surge up a series of inclines just after the halfway mark to break clear and win in two hours 26.20 minutes to grab Japan's 13th gold.
The Japanese have also won six silvers and seven bronzes.
The Chinese set a goal of 20 golds at Athens, and in many sports brought untested young athletes rather than proven talents to gain experience for 2008, when Beijing hosts the Games.
After decades of war, revolution and political boycotts, China returned to Olympic competition in 1984 at Los Angeles.
In two decades, they have risen to eclipse Russia and challenge the United States in many sports, save athletics and swimming.
Chinese delegation team manager Xiao Tian acknowledged the 100th medal -- which came on a day when back home the country was marking the 100th birth anniversary of Deng Xiaoping, the late architect of China's economic opening and modernisation.
"But we won't celebrate until the Games are over," Tian said, urging the team to resist complacency.
Wang Hao will attempt to give China another Olympic sweep in table tennis when he takes on South Korea's Ryu Seung-min in the men's final on Monday.