Question: are zekrom and reshiram shiny locked?
Answer: Keep in mind that some Pokémon are Shiny Locked. Shiny Locked Pokémon cannot be encountered as a Shiny if that particular encounter with them is Shiny Locked. Here's a list of the Pokémon that are Shiny Locked, by game: Black & White: Reshiram, Zekrom, Victini.