I dont think a shovel and 3 tanks is even possible.
Can you add a spectator room for the shovel and tanks room?
It's easy. Just jump around and beat them down. I've killed 2 tanks lead pipe, shouldn't be too difficult.
You know, challenges are SUPPOSED to be possible to be completeted.
And it is. Just hard.
Can you do it yourself? Without any advantages above the normal player?