As far as I know, there isn't a podcast like client or note kind for Nostr yet, so perhaps the differences could be considered for maximum compatibility.
Not that familiar with zap.stream yet.
It is an interesting use case, but as I can see, the Podcasting 2.0 format is quite different and has (obviously) specific fields. It could be interesting for something like https://zap.stream
Btw, I just moved from RSS to Atom, because it seems more supported by the classic feed readers.
Discussion
I will investigate, thanks for the hint!