Mark Zuckerberg is clearly taking his potential fight with Elon Musk seriously ... he revealed Tuesday he's already getting in training sessions with some of the UFC's biggest stars -- and he's looking damn good while doing it!!
TMZ Sports has learned ... both Israel Adesanya and Alex Volkanvski flew to Zuck's crib in Northern California following Saturday night's UFC 290 showcase in Vegas -- and almost immediately, they got to work with the Meta honcho on the mats to prep him for a possible tilt with Musk.