@ton Neat. I'm also trying out Zettelkästen, and I've found it useful in terms of improving my understanding as I read around a given topic. Atomizing concepts and explicitly looking for connections is a great way to clarify one's thinking (and it would still be powerful even if I were to throw the notes in the bin afterwards).
However, I haven't done it long enough to actually get to the "ohhhhh look at this unexpected connection!" moment. Great to read about your experience.