District and Sessions Judge Mohammad Shahenur delivered the verdict on Tuesday.
The convicts are Zakia's daughter-in-law Sharmin Akhter, 27, Jashim Uddin, 30, from Andhar Manik village in Laxmipur Sadar Upazila, Jamal Hossain, 28, from Laxmipur District's Chandraganj, and Nazim Uddin, 30, from Chandpur District's Bakhorpur Upazila.
All of them are absconding, said Public Prosecutor Jashim Uddin.
According to the case dossier, Zakia, a native of Sadar Upazila's Dharmapur village, was strangled to death by Sharmin on July 14, 2016, after she found out about her daughter-in-law's extra-marital affair with Jamal. Jamal and two others abetted the murder.
Later, Zakia's younger son Khorshed Alam as plaintiff started a case against Sharmin and four others for murder.
The trial proceedings began after Laxmipur Sadar Police SI Morshed Alam pressed charges against the suspects on July 2, 2017.