I wasn't looking at the original quote when I wrote what I wrote above, FWIW. And I wanted to avoid the instinctive inclination to write "he", so I went with "ze" because using "they" for singular case always feels forced and awkward to me. But yes, that would have been fine as well. It was a choice I made at a moment in time, not something that I spent a lot of time analyzing and debating. :-)