Here's why:
* He's not a recurring character: Zook is the main antagonist in Pokemon XD and serves as the final boss. Once defeated, he's removed from the game's narrative.
* No post-game content: Pokemon XD lacks significant post-game content like rematches or extra battles.
However, you can encounter other trainers and challenge them for battles in the game's post-game. This will allow you to test your skills and potentially earn some valuable rewards.