Abu Az-Zinad أبو الزناد is 'Abdullah ibn Dhakwan عبد الله بن ذكوان a scholar of fiqh and hafidh of hadith from Medina who was born before the death of ibn' Abbas and met Anas ibn Malik and ibn 'Omar, so he is a (young) tabi' y. He died in Ramadan 130 a. H. among his prominent students you may find imams such as Malik, al-Laithi ibn Sa'as and Sufyan at-Thawry who considered him amir al-Mu'minyn in hadith. Al-Laith reported that when Abu at-Zinad entered the mosque of the prophet () he was in such a big company (in his case of students) as if he was the Sultan.
Maybe a reason why he was more known as Abu Az-Zinad is to avoid confusion with the qar'i ibn Dhakwan the student if ibn 'Aamir who died 174 a. H..
As for al-A'araj (the lame or criple) الأعرج this is the nickname of the known hafidh of hadith, faqih and qur'an reciter and scribe (of Moshafs) 'Abdurrahman ibn Hurmuz عبد الرحمان بن هرمز he died 117 a.H. in Alexandria in Egypt where he was for an expedition. He is known for his participation in Jihad and was a teacher of prominent scholars such as Abu Az-Zinad and az-Zuhri.
He learnt qira'a directly from Abu Hurairah, 'Abdullah ibn' Abbas and 'Abdullah ibn' Ayach and he is one of the teachers of Nafi'i ibn Abi Nua'im (one of the 7 qurra' and teacher of Warsh and Qalun) . He is a tabiy too.
See also Should we speak about someone (when he is bad, and I'm sure about that) to aware others?.
The above is a short summary from different biographical sources such as Siyar a'alam an-Nubala'.
Note that the chain Malik from Abu Az-Zinad from al-A'araj from Abu Hurairah from the prophet () is the most sahih Hadith chain via Abu Hurairah.