إِيَّاكَ نَعْبُدُ.
Meaning: You alone we worship.
Parsing: iyyāka is an independent pronoun occupying the accusative position as fronted object; naʿbudu is an indicative present verb; its concealed subject is naḥnu.
إِيَّايَ تَقْصِدُ.
Meaning: You seek me. Iyyāya is a fronted object; taqṣidu has a concealed subject (anta).