If you are asking about current patch lobotomy, you have to trigger the "warning: intruder detected flushing interior" message then clip outside the earthmover and hit an invisible trigger by the door past where you do the security system fight, this enables the trigger for the boss to spawn while you are outside the earthmover. From there just hit the trigger under the earthmover's chin and it will die. If you are having a hard time seeing I recommend turning up gamma.
Both clipping into and out of the earthmover are done by getting on a frozen rocket placed facing down at a 45 degree angle against the wall. Then firing a rocket, jumping and whiplashing all at the same time. The screenshots show which walls you need to clip through.
If you have not seen ULTRAKILL is finally having a speedrunner competition for real money!!! It starts in about four hours from the time I am making this news post, in fact its probably already started when you are reading this so click the challenges widget on the right and read up on the rules and
