I tend to agree with this assessment of his Mandarin more than the gp's. As a native speaker, I must disagree when gp says: "He does decently enough. There are errors, but it's not hard to understand what he is saying -- especially for a sympathetic native listener." Large parts were incomprehensible to me (in part due to the audio quality), and the host's repetition of what Zuckerberg said--he does this many times--were a breath of fresh air. Maybe the experience between gp and myself was like the one mentioned in the Foreign Policy article [1]. The author mentions that he was an adult learner of Chinese and was able to understand Zuckerberg's Mandarin better than a native Mandarin speaker who watched the video with him.

I do admire the energy Zuckerberg is putting into learning Chinese. It's not an easy language to learn. What I found interesting was the sycophantic praise from ABCs in the comments section with gems like: "As much as we are impressed with your Chinese, you made a lot of the ABCs here feel ashamed."

[1] http://blog.foreignpolicy.com/posts/2014/10/22/mark_zuckerbe...