If you manage to destroy one of the middle sections, everything behind that section (in the chain) will explode in a lovely chain reaction. It might be a smidge too durable if that didn't happen, because the green has a grand total of 1350 health to be depleted, whereas the yellow has a staggering 2300 total health. For comparison, the first boss has 900 health, and the second has 3000. Oh, and at the moment, the third boss has 5000 health. :U