I would also rule that the planetaar sees through lies. Glibness states "magic that would determine if you are telling the truth indicates that you are being truthful." Meaning non-magical methods can still overcome the protection. If I tell you that you can't hear anything, you can still tell that you heard me say that. You are protected from zone of truth, not from a planetar innate ability to tell falsehoods.
That said, I would rule any non-lie deception is still just as effective as normal. If you want to mislead him, omit details, or other forms of deceptions which are not outright-lies. Then you are fine. "The guy who did it was almost 6 foot tall humanoid with brown hair." "Can you tell me more?" "I wouldn't feel safe if I did." Perfectly non-lying way to answer questions about how yourself was they guy who did it.
That said, I would rule any non-lie deception is still just as effective as normal. If you want to mislead him, omit details, or other forms of deceptions which are not outright-lies. Then you are fine. "The guy who did it was almost 6 foot tall humanoid with brown hair." "Can you tell me more?" "I wouldn't feel safe if I did." Perfectly non-lying way to answer questions about how yourself was they guy who did it.
