The title of this talk is 'zero knowledge succinct non-interactive arguments of knowledge for laypeople', yet the speaker (at 1:40 in the talk), says he won't be able to explain how they work.

ZCash, at least for the first 3 builds, did not have their primary feature (fully anonymous transactions) working. I don't believe thats fixed yet (is it?). How they missed their primary feature being broken before releasing, I have no idea.