I can't praise Zhi's teaching enough. Calculus was pretty non-intuitive to me at first. Fortunately, Zhi has an approach to explaining the intricacies, purpose and applications of the subject that brings it into perfect clarity. He is infinitely patient of questions and always extremely well-prepared.
If you are a reading this review and are concerned over the issue of instructors teaching in their non-native language, let me assuage your fears (in this instance). Though Zhi's English is not word-perfect, it is excellent, and his lectures are well-delivered. Zhi was never unable to communicate a point effectively in my experience.