Chu Li sincerely wanted to learn from Zheng Yanwu. He thought that the level of Zheng Tianhe's White Tiger Power was too low. By contrast, Zheng Yanwu was a hundred-year-old hidden master and he must have a high mastery of White Tiger Power. If Chu Li could learn something from him, it would be enough for him to cultivate for the time being.
Next time, he would seek another opportunity to obtain the key points of White Tiger Power.
If he was lucky, Zheng Yanwu might have achieved the highest boundary of White Tiger Power. Chu Li could then save some time and effort.
He refused to fight Zheng Yanwu directly as he wanted to observe the latter's cultivation of White Tiger Power. Otherwise, had they fought and Zheng Yanwu died, Chu Li would no longer have the opportunity to learn the White Tiger Power.