Sorry but because you have trained it already it's impossible to tell, unless you know the exact EVs it has.
You'll have to wait until you get to level 100 and check it against this page: http://pokemondb.net/pokedex/zekrom
Under "Zekrom stats" check the numbers on the right and see where yours fit in. If they are in the middle then the stats are pretty good.
Note: you can't get near the maximum in all the stats because of EVs and natures. But if you are close on a couple of stats that is great.