Judge Md Mujibur Rahman of the Anti-Terrorism Special Tribunal set aside the date on Sunday after the state and defence finished their arguments.
The other suspects are Akram Hossain alias Hasib, Moinul Hassan Shamim alias Samir, Abdur Sabur Samad, Khairul Islam, Abu Siddik Sohel, Mozammel Hussain and Sheikh Abdullah.
They are all members of the banned militant outfit Ansar Al Islam, according to the police.
Six suspects are behind bars while Ziaul and Akram absconding. The six entered a plea of not guilty during the framing of the charges in October 2019.
It came months after Islamist militants murdered science writer and blogger Avijit Roy, the first death in the wave of violence against secular writers in Bangladesh.
Dipan’s Jagriti Prokashony published Avijit’s books. Another publisher of Avijit’s books, Rashid Chowdhury Tutul, survived an attack on his office in Lalmatia.
The police said Ziaul masterminded and ordered the killing of Dipan. Zaiul has been charged in several other cases over similar attacks.