As the sibling comment says, neither gp comment nor this post are zero-knowledge. But in addition to the definition given in sibling comment, here's another ne

As the sibling comment says, neither gp comment nor this post are zero-knowledge. But in addition to the definition given in sibling comment, here's another necessary condition of a zero-knowledge proof: it must be possible to forge transcripts (i.e., one party writing both sides of the interaction) of a zk proof even without possessing the secret.