Which green Zen is illegal?

I'm intrigued by the mention of a "green Zen" that is apparently illegal. Could you please clarify what exactly is being referred to here? Is it a specific cryptocurrency, a financial product, or perhaps a type of investment scheme? And why is it considered illegal? Is it due to fraudulent practices, regulatory violations, or some other reason? Understanding the context and specifics of this "green Zen" would greatly help in addressing the question of its legality.