Data from both auction houses was used to score the sales on the HENI Auction Index.
The protest comes after the university closed the artist's show several months early.
Christie's spring sales in Hong Kong totaled $113.4m and scored a B+ on the HENI Auction Index, a third straight improvement.
Zhang's work takes the form of a visual letter to her daughter
The show is inspired by an 18th century painting imagining the Bank of England as a Roman ruin.
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