πεύθετο γὰρ Γαίης τε καὶ Οὐρανοῦ
ἀστερόεντος οὕνεκά οἱ πέπρωτο ἑῷ ὑπὸ παιδὶ δαμῆναι,
καὶ κρατερῷ περ ἐόντι, Διὸς μεγάλου διὰ βουλάς
--- Theogony 463~465
For he had heard from Earth and starry Sky that, mighty though he was, he was destined to be overpowered by a child of his, through the plans of great Zeus. (Loeb Classical Library)
For he learned from Gaia and starry Ouranos
that it was fate that his own son would overthrow him,
although he was powerful, by the plans of great Zeus. (Richard S. Caldwell)
Both translations read to me like a prophecy that Kronos was destined to be overpowered by Zeus through his future plans. But people claim it means that Zeus willed Kronos' destiny before he was even born.
During my research I found at least some Greek authors (Stauros & Blachos) who seemed (I don't know much Greek) to agree(?):
απ' την βουλη του μεγαλου Δια*
from the will/plan of the great Zeus*
*Σαν υα προυπηρχε η βουλη του Δια απο την γεννηση του. Η βουλη του Δια ταυτιζεται εδω, με την Μοιρα, στοιχειο αχρονο.
*As if the will of Zeus had existed since his birth ...
More different translations:
despite his strength, as the will of great Zeus decreed. (Norman O. Brown)
no matter how mighty Cronus was,
deliberate action by a great god would win out. (C.S. Morrissey)
powerful though he was, through the designs of great Zeus. (M.L. West)
That his own child would conquer him, powerful though he was, And this was bound to happen through the plan of mighty Zeus. (Catherine Schlegel & Henry Weinfield)
that it had been ordained for him,
for all his great strength,
to be beaten by his son,
and through the designs of great Zeus. (Richmond Lattimore)