Zamora joined politics during the
administration of
Ferdinand Marcos at the Presidential Economic Staff, as the chief economist from 1966 to 1967, senior information officer from 1967 to 1970, Technical Assistant Staff Service Unit from 1970 to 1972. He later served under the
Office of the President as Acting Assistant Executive Secretary from 1972 to 1974, Assistant Executive Secretary from 1974 to 1975, and Presidential Assistant for Legal Affairs from 1975 to 1978. In
1984, when the constituency in the
Batasang Pambansa was modified—to elect members by province and cities, instead of regions—Zamora ran for the parliamentary seat for
San Juan–Mandaluyong but lost to opposition candidate
Neptali Gonzales. When
Congress was restored under a
new constitution in 1987, he ran and was elected representative of the
lone district of San Juan–Mandaluyong in
1987 and
1992, and as representative of the
lone district of San Juan in
1995. He was also elected as
House Minority Floor Leader during the
10th Congress of the Philippines. Barred from seeking another term in 1998, Zamora helped his long-time political ally and townsmate
Joseph Estrada in his
presidential bid in 1998. Estrada later appointed Zamora as his
Executive Secretary. Concurrent to
president Estrada's impeachment trial, Zamora resigned from Estrada's cabinet in late December 2000 to run for representative of San Juan again in
2001, although he clarified that it was not done to abandon Estrada. He would be reelected again in
2004 and in
2007, for three terms. In the
14th Congress (2007–2010), Zamora was also elected as House Minority Floor Leader. After stepping down from Congress upon being term-limited in 2010, Zamora served as a member of the Board of Directors of
Nickel Asia Corporation, a mining company founded by his brother Manuel Jr., from 2011 to his retirement from the company in 2013. He also served as Chairman of the Rio Tuba Nickel Mining Corporation and later of Cagdianao Mining Corporation, subsidiaries of Nickel Asia Corporation. He was re-elected in
2016 and
2019. He would retire from politics at the end of his term in 2022, according to his son
Francis, who was
elected Mayor of San Juan in 2019. He was succeeded by his daughter,
Bel Zamora; his other daughter,
Pammy Zamora, also assumed office as representative of
Taguig's
2nd district on the same year. ==Personal life==