I have a friend who is an agnostic. Interestingly, he made a point of me understanding he is an agnostic and not an atheist. Hmmm. He recently discovered that Catholics believe that the Eucharist is the Real Presence. To him, this is insanity.
The Bible is myth so I can’t go there. I came to the conclusion the only way I could reach him is through his interest in math and science. EWTN has a wonderful series, way beyond my capabilities, proving the existence of God through physics etc. Fascinating to me and I don’t even understand what the priest is saying.

So I would direct my friend to that series and then discuss what he thought.
Another idea that just came to mind is check out Marcus Grodi’s web site. He does THE JOURNEY HOME on EWTN. He might have a the story of a believer in Eastern philosophy who converted to Catholicism. You might give him the convert’s story to read.