أَكَلَ الْكَمْثَرَىٰ يَحْيَىٰ
Translation: Yaḥyā ate the pear.
أَكَلَ: past-tense verb.
الْكَمْثَرَىٰ: advanced accusative object; its fatḥa is estimated.
يَحْيَىٰ: postponed nominative subject; its ḍamma is estimated.
Both cases are hidden, but the meaning supplies the clue: a person eats the pear, not the reverse. Thus semantic context allows object-first order.