Why so serious? >.< This is better than most comics i have seen... Its a hell of a lot more creative than a lot of the other ones which seem mostly like clones. I like it :D...
Trolling isn't sexy.
Also, Steampunk isn't all about 'coal' power. It has a lot to do with clockwork also. It could also be speculated that in a world where a wolf can be bio-luminescent (to which the name Zombie seems very fitting) it may be found that there is a metal which happens to have an effect on gravity where it floats in mid-air. Possibly some effect where it converts gravitons to anti-gravitons to allow an effect of floating, but not the force to go forward which would explain the engine on the back of it. Due to near weightlessness it would be easy to propel forward, possibly using a type of ion engine. A true artist doesn't criticize immediately on not making sense, he first thinks on if it really does make sense in a world that may not be our own. And if it is fiction, y'all should start thinking out of the box.
And, by the way. If you want to get all technical, in THIS world flesh cannot be radioactive because it needs to have an atomic mass that is so large that it decays, meaning he cannot be radioactive. And bio-luminescence is a rather common phenomenon. If you don't believe me, walk out your back door at night in spring sometime if you live in the country. When you see the glowing flashing things in the air... Those are bio-luminescent... nope, not magical fairy dust.
As I stated before, there may be a substance which acts as anti-gravity, or more likely some how block gravity making it weightless and able to suspend itself in air. If you're skeptical and think its a dumb idea, you should read the book "The First Men in the Moon." by H. G. Wells.