Basically Zekrom with Fly.
With Dragon Type and electric type moves Zekrom has great coverage spare Ferrothorn, Exadrill, Magnezone and Steelix. However for the latter three Zekrom has only two options Rock smash or focus blast, both are iffy at best, Ferrothorn on the other Hand can be dealt with through fly, ferrothorn will likely be the new forretress, so it will be pretty common. Fly provides Zekrom with a way around this. also Zekrom sports a rare 4x resistance to thunder so even it the rain, it flies safely.
PS Smogon lists ferrothorn as one of zekroms counters so this would be even more viable.
Jolly / Adamant
252 AT 252 SP/HP 6 HP/SP
Bolt strike/Fusion BoltFly
Some other Move/ Dragon Tail/ Volt Change/ Etc
besides the fact that It give the opponent a chance to switch out, which I see as the biggest threat to this set what other comments do you have on it?