إِنَّ إِلَيْنَآ إِيَابَهُمْ
Sentence structure
إِنَّ opens an emphatic clause. إِلَيْنَآ is the fronted predicate and إِيَابَهُمْ the delayed noun of إِنَّ; attached هُمْ is a possessor.
Ayah summary
Surely everyone must return to Us alone.
إِنَّ — Indeed
Grammar: An accusative/emphatic particle opening a nominal clause.
إِلَيْنَآ — to Us
Grammar: إِلَى is a preposition and attached نَآ a first-person-plural genitive pronoun; the phrase is the fronted predicate of إِنَّ.
إِيَابَهُمْ — (will be) their return
Grammar: إِيَابَ is the delayed accusative noun of إِنَّ; attached هُمْ is a third-person masculine-plural possessor.