You capture both Kyurem and Zekrom in Pokemon black2. Later in the game, you will get DNA splicers that allow you to fuse either Zekrom and Kyurem into Black Kyurem, or convert Reshiram and Kyurem into white Kyurem. To get Kyurem, look in the Giant Chasm, and for Zekrom, just follow the Zoruark.
