"A "ballet" flat," the actress wrote under the photo. An innocent enough description of the footwear. That is until you consider the ballet-related drama Kendall Jenner has dealt with this week. Recently, Jenner has faced criticism for a Vogue España ballet-themed video she starred in. Professional dancers weren't impressed seeing Jenner don dance wear, without any real training. They felt the video disrespected all the hours they've committed toward perfecting their relevés.
The quotes around ballet in Zendaya's caption seems to strongly suggest this was shade, though why she would want to call out Jenner is unclear. Perhaps she felt some solidarity with the ballerinas as a fellow dancer?