What differs between «زَيْدًا عَرَفْتُهُ» and «زَيْدًا عَرَفْتُ»?

Fronting the Object: Correction, Restriction and Ordering of Complements

• The second is an intransitive verb
• Zayd is nominative subject in the first
• There is no syntactic difference
• The first includes a pronoun referring to the fronted noun