Standing tall at 8.8 km, Zeeman Mons on the Moon competes with Earth's Mount Everest.
Zeeman Mons rises 8.8 km above the floor of the crater within which it resides, the Zeeman crater (duh). While mountains on Earth take millions of years to form under the slow process of tectonic plates colliding, mountains on the Moon form near instantly!
Mountains on the Moon typically form when an asteroid/comet impacts the lunar surface. The impactor hits the surface and compresses the material, which then rebounds back up to form a mountain! Many central, high mountains in all large craters on the Moon are formed in this way.
Imagine a mountain rising as high as Mount Everest, but formed near instantly instead of taking millions of years! That's lunar geology for you. Landing in large craters and studying their mountains from material that has slid down to the crater floor is exciting for future lunar landing missions.