I don’t know exactly what the use cases for nocache and from_file are, so it’s hard to know whether it’d ever be a problem if these were unpicklable.
I wonder if you could have an opaque RawZoneInfo object that behaves like a nocache ZoneInfo and is pickled by value, and have regular ZoneInfo be a very thin wrapper for that (maybe a subclass with no extra fields) but with by-key pickle behavior?