I was successful with the following approach:
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×Isolate the northern nests by blocking the path with the south-most nest of the northern part.
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×Go into the south part as soon as the yellow door opens. Kill all nests on your side of the water expect the one in the south west corner. After killing the nests, go to the checkpoint and decimate the WSs until you can get to the other side. Try to find a movement pattern which kills 2 WSs in 3 moves.
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×After reaching the other side, kill the two nests. Leave the corner nest alone again.
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×Rush to the orb that stops the timer. Clean up everything and leave the room.