Ozai likely harbors a deep grudge against Zuko for contributing to his downfall. More so, he might feel a subconscious jealousy toward Zuko, as he now has the title of Fire Lord and control over the Fire Nation. Despite Ozai's apparent pride in Azula's prowess, it is clear that he holds little true, unconditional love for his daughter.
Ozai enjoys to have some semblance of control over Zuko even in his helpless state; particularly, he is amused at his son's inner dilemmas on how to rule the nation as well as his desire to find Ursa. He also commends Azula on being able to trick her brother even after her own fall from grace.