Depends entirely on the situation. If Baldur has his invulnerability, I believe it would be a Stalemate since Baldur can’t die but at the same time, there’s nothing in Baldurs abilities or arsenal that could kill Zeus. Zeus absolutely REFUSED to go down in God of War 3 and that was against PRIME Kratos. But, if Baldur doesn’t have his invulnerability, then Zeus wins with the force of a thousand curbstomps lmao
Honestly, most of the Greek Gods would just fight Baldur to a stalemate if Baldur has his invulnerability. The only Greek God that I think would come out with a win instead of a stalemate would be Hades and that’s only because Hades could use his claws to take Baldurs soul.
All that being said, I think Baldur without invulnerability is about Ares level or just below. Baldur is pretty strong and is more than likely the 3rd Strongest Norse God behind only Thor and Odin.