جَاءَ زَيْدٌ عَيْنُهُ — Zayd himself came.
جَاءَ: past tense verb.
زَيْدٌ: nominative subject.
عَيْنُهُ: nominative semantic emphasis; ʿayn is the first term of iḍāfah and -hu its genitive complement.
This teaching example uses ʿayn as “the person himself,” not as an eye or object.