The previous season of 'Zero Duel Masters' was set in an alternate universe, so this season's plot is a continuation of the Duel Masters Charge. It follows the aftermath of the duel of Shobu vs. Zakira. (Source: Duel Masters Wikia)
9Anime is the best site to watch
[RAW] Duel Masters Zero SUB online, or you can even watch
[RAW] Duel Masters Zero DUB in HD quality. You can also find
anime on 9Anime website.