AnyCubic MEGA ZERO - Supplements to Leveling

Leveling
After the leveling of the fourth point, you must choose "Next corner"
to return to the first point to level again. Please adjust the 4 points
of the platform 2 or 3 times to ensure leveling result is OK,
otherwise the platform could be scratched.
2. Supplements to leveling
Case @: After homing, the nozzle is still much lower than the platform,
even if the 4 nuts underneath are fully tightened.
Case @: After homing, the nozzle is still too far from the platform, even
if the 4 nuts underneath are fully loosened.
How to solve this:
Case ®: adjust Z limit switch up.
Case @): adjust Z limit switch down.
After adjusting, please home and level again.
Z limit switch