I'll give Zizek credit and assume he has entered the dhamma through one of the over 84,000 gates. Regardless, Zizek has a skewed interpretation of śūnyatā.  He perhaps is showing early symptoms of what Zen calls "sunyata disease", or zen sickness.
That is to say, Zizek has only glanced over - not tamped down his ego - the first [turning of the dhamma wheel][1], vaguely understands - in the mind-only sense - the second turning of the wheel (sunyata as void, an abyss, a nothingness), and arrives at the third turning without fanfare - lacking Buddha-nature.


To be clear, the second and third turnings are merely insight. And in Zizek’s case, not having done the work of the first turning, a [corruption of insight][2] (crimes against wisdom). 




  [1]: https://www.learnreligions.com/three-turnings-of-the-dharma-wheel-450003
  [2]: https://www.accesstoinsight.org/tipitaka/an/an04/an04.170.than.html