Which contrast between «زَيْدٍ» and «عُمَرَ» is correct?

Noun Case Classes: Type 3 — Diptote (Ghayr Munṣarif)

• Both are always accusative
• Zayd is indeclinable and ʿUmar declinable
• In genitive Zayd takes kasra, ʿUmar normally fatḥa
• Prepositions do not govern Zayd