Basically, Steampunk is a sub-par genre, literary wise, and, in the broadest of terms, is for complete losers and pot heads.
Machinery should be sexy, quiet, deadly. Not clunky, dirty, loud, prone to break at a moments notice. Machinery should be like a mountain, it simply is. It should NOT be like the pile of steaming poo you just stepped in, thanks to your neighbor not taking care of their misbegotten wretch of a walking chinese meat dish.
Gasmasks, zombies, airships and burrowing machine monstrosities are all SEPARATE things, and should NOT be combined. Gasmasks belong in WWI or WWII history books. Zombies belong in either ultra-violent, ultra-poorly written slasher books or ultra-modern scientific fiction. Airships should stay in blurbs about the Hindenburg. And digging machines, well, they belong off planet, in the FUTURE!
So, Skynet, if you ever read this, forget John Connor. For the love of efficiency, come back and kill of the creators of Steampunk. Maybe we humans will then embrace you as an enlightened sentient being. I know I will!