Zaman joined the judicial branch of the Bangladesh Civil Service on 22 February 1984 as a munsif.[1] He was promoted to Senior Assistant Judge and Joint District Judge.[1]
Zaman was appointed an additional judge of the High Court Division on 31 May 2018.[1] In July, Zaman and Justice Obaidul Hassan rejected the bail application Mahabubul Haque Chisty, former audit chief of the Farmers Bank.[5]
In February 2019, Zaman and Justice Obaidul Hassan denied bail to Tufan Sarker, Sramik League convener of Bogura District, in a rape and torture case.[6] Zaman and Justice Obaidul Hassan fined Md Feroz Alam, a former Feni District Court Judge, for contempt of court for failure to provide protocol to High Court Justice Syed Amirul Islam.[7] In March, Zaman and Justice Mamnoon Rahman withdrew the bail to former Awami League leader Ruhul Amin for ordering a rape for withholding information in bail appeal.[8] Zaman and Justice Obaidul Hassan rejected the bail application of former Prime Minister Khaleda Zia in the Zia Charitable Trust corruption case in July.[9]