are you sure it realy works (i cloned my original Zekrom/reshiram and marked it as shiny - normaly all other mons work with that), as i tried to connect to DW it says game sync out of energy.....and that is what could not be, as the game allmost has passed the 24 hrs limitation and i think i´ve damaged the game with that now!?
Important: I do not recomend to catch shiny Zekrom/Reshiram, Meloetta (they may harm your Game, so that you get either an 13xxx error code or that - like in my case the Game Sync has run out of energy, even if i did not visit DW for days or so.....hope the erase pokedex-data code helped me to get back access to DW in Black1 in 1-2 Days...)
So if you want them shiny in your Pdex (specially for BW2) do only meet them in the wild and kill them or flee, as only Victiny (yes the event one i marked shiny), Keldeo (also cloned and marked shiny), Tornadus, Thundrus, Landrus, Kyurem, Cobalion, Virizion and Terrakium seem to be the only ones to be not checked (in B/W.....don´t know how it works on B/W2).
"Wait....you.....did....not mention Genesect".......that´s true, as i cheated this one in Black1 and as shiny, and it did not harm the accessibility of the DW - but I do not know if it would if someone tries to mark the Event-one in box to become shiny (so I do not recomend to do so) - so if you want this one shiny in dex too, only meet in wild and then get the hell out of the battle (flee or beat it)!