حزب التحرير
In 1951 he moved to al-Khaleel and worked as a teacher in Osama Bin Munqiz School. Here he met Taqiuddin al-Nabhani in 1952. He joined Hizb ut-Tahrir in 1953. After the death of Taqiuddin al-Nabhani in 1977, Zallum was chosen to be the global leader of Hizb ut-Tahrir. He remained the head of Hizb ut-Tahrir until he resigned on March 17, 2003. Zallum died on April 29, 2003.