In Dragon Ball Z budakai 2 how do you get a z item

Well, if you beat a main character in the end of the story mode, you get a Z item. For example, you beat Vegeta in Oozaru form, and you get power ball. You can use this power ball to unlock the Oozaru form of Vegeta, Nappa, Radditz, Bardock, Gohan and another guy whose name I forgot. You may also get Z items if you achieve perfects and one hit KOs etc. You jus gotta explore, man.