being the rarest we haven't seen anyone eating a mythological zoan just yet and my theory is that it awakens only when the subject is strong enough to withstand it. look at momonusoke problem his devil fruit is artificial and it acts like a mythological one and he hears its voice plus he cant handle it. maco seems like someone who handled himself without the power of devil fruit a long time... just speculation. now the real question is does the stone effects occur from eating the devil fruit or from the fact that you have the power of the devil fruit? a semi-philosophical question that has no definite answer just yet. if zoro lucks in observation and flexibility and flowing harmony then his devil fruit will have those criteria. I believe that he has the ghost fruit or some strange bird fruit for that matter. maybe a wyvern. I would want that one! what do you guys think?