First and foremost: DON'T APE OUT. This may feel counter-intuitive, because this game does such an amazing job in allowing you to let out your inner Ape. But when it comes to this level, densely packed with enemies and uncomfortably small spaces, you would do yourself a great favor by reminding yourself that it is you, a person, who's in control here. Try not to fall into the game's trick that it does with its fast, rhythmic music; take your time, approach enemies slowly, there is no need to rush anywhere. This level is simply too packed to breeze through.

Second tip: you can't kill 'em all. And you don't have to! Just stick to one wall of your choosing (on the top or on the bottom). When you're against the wall, that's half less enemies to deal with. Those on the other side tend to remain there, unless you attract them - so don't. However, those on the side you've picked have to be disposed of, don't leave them walking around your territory (see tip #3).

And lastly, remember that after you Break In, you'll have to Break Out. Sticking to the wall means that you'll unavoidably pass four elevators, and the enemies that will go out of them will be waiting for you on your way out. Dispose of them with a single blow and move along quickly, before more spawn. And if they do - they'll remind alongside the elevators, so you'll know where to expect them on your way back. On my winning attempt the enemies that spawned from the elevators off-screen were the only ones I encountered while Breaking Out.

That's it. Hope someone finds this helpful!