What does it mean that the books of Abu Dawud al-Tayalisi belonged to Amr ibn Marzuq, and that Amr transferred his books after Abu Dawud's death, and what does it mean that the audition of Abu Dawud and Amr ibn Marzuq from Shu'bah was one and the same, and what is your comment on Ali ibn al-Madini's softening towards Amr and Ahmad ibn Hanbal's astonishment at that?

The meaning of "Muslim ibn Ibrahim" is that Amr ibn Marzooq owned the books that were with Abu Dawud Al-Tayalisi, and he left them with him because he was preoccupied with ghazw (military expeditions), then retrieved them after Abu Dawud's death. Abu Dawud and Amr ibn Marzooq's hearing from Shu'ba is considered one because they both sought knowledge and attended his مجلس (gathering) together. Imam Ahmad refuted Ali ibn Al-Madini's aspersion against Amr, and he was authenticated by Imam Ahmad himself, as well as by Ibn Ma'in, Muhammad ibn Sa'id, Abu Hatim and his son. Ibn Hibban mentioned him in Al-Thiqat (Reliable Narrators), and Al-Bukhari narrated from him in conjunction with another narrator. Al-Albani authenticated his hadith (definition).