‘So Achilles prayed
and Zeus in all his wisdom heard those prayers.
One prayer the Father granted, the other he denied:
Patroclus would drive the onslaught off the ships-
that much Zeus granted, true,
but denied him safe and sound return from battle.
Once Achilles had poured the wine and prayed to Zeus,
he returned to his shelter, stowed the cup in the chest
then took his stand outside, his spirit yearning still…’
– Homer’s Iliad, Book 16
Zeus is the Father and king of Gods and men. He protects the weak. He upholds the law. In layman’s terms, He’s the big boss of just about everything. There are instances in the mythology where He recognises the authority of others (such as Nyx), but on the whole, He is supreme. It is therefore logical to presume that He hears any and every prayer. As is shown in the Iliad, He cannot grant every prayer as sometimes Fate gets in the way but it’s safe to say that every prayer is heard.
I pray to Zeus. I pray that His great and mighty will be done, not mine, as for me right now, Father knows best.