Prof Zhang is a great person. He is kind and funny. However, his accent makes things hard to understand, and he has a very quiet, introverted voice for a class that has 200 students in it. While my grade is mostly due to my lack of effort in studying the material, the effort was lost due to his extremely unengaging class. I felt no merit or reason to go to his lectures because I felt like I did not learn anything. The youtube math channels helped me much more, and only if I studied harder and earlier for the final, I would have ended with a much better grade. That said, he is a horrible instructor, and I would strongly recommend you choose another option if available or take it another semester. You should only take this class with him only if all of the conditions below are met:
1. You need to take Math 31B this quarter
2-1. Your only option or time available is this class
2-2. your other option is Ocal
3. You are willing to self-study via youtube

If these conditions are met, it is ok to take this course since you have no other choice.

That said, I publically condemn the UCLA Math Dept. for purposely putting the worst math instructors at UCLA for this significantly important class for many majors. Also, I originally had Li, but they just swapped him with Ocal, and then swapped again with Zhang. They should do this before students start course registration since the instructor is one of the biggest factors in choosing a class.