I figured this out with a clan-mate first time we attempted this.
We accidentally triggered a delayed spawn, and we wanted to know how we did it, so we kept experimenting till we found the cheese!
Basically what the cheese is:
Round 2 and 3 have a delayed hive spawn, so you're able to finish off the bombs before the wizards and boomers come out to annihilate you.
https://www.youtube.com/watch?v=iy5vm668VwA
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Really? Cheesing the lvl 34? Its not that hard. Yes its challenging but for fuks sake just try and beat it normal. How are you going to attempt 35 if you're already cheesing 34. So bad