Van Zeil became a member of the House of Representatives after Gerard Veringa was appointed as a member of the Council of State, taking office on 1 February 1972 serving as a frontbencher chairing the parliamentary committee for Kingdom Relations and spokesperson for transport, aviation, Kingdom relations and deputy spokesperson for social affairs.

Van Zeil was also appointed State Secretary of Social Affairs and Employment and dual served in those positions, taking office on 12 June 1982.

After the 1982 general election, Van Zeil returned to the House of Representatives, taking office on 16 September 1982.

After the 1986 general election, Van Zeil again returned to the House of Representatives, taking office on 3 June 1986.

Van Zeil semi-retired after spending 20 years in national politics and became active in the private sector and public sector and occupied numerous seats as a corporate director and nonprofit director on several boards of directors and supervisory boards (Netherlands Bible Society, Transnational Institute, and the Catholic Scouts) and served on several state commissions and councils on behalf of the government (Cadastre Agency, Public Pension Funds PFZW and KPN).