Looks like the Zaplighter really is just a combination of NIP-57 (Lightning zaps) and NIP-84 (Highlighter).

You would just need to create a highlight event on the individual image/media or passage and then list that event in the "e" tag of your zap request event. I think.

And then display the zap directly on the highlighted bit, so that it's clear which item you zapped.

You could do the same with reaction events (NIP-25), I guess, so that you can👍 parts of notes.

Kind of confusing, tho, as you'd be zapping and reacting on your own note. 🤔