It's marketed as a co headlined show, but quite clearly, nobody can deny it is in fact Kendrick's show.
However,
The tour is named Grand National Tour (reference to Kendrick album), the aesthetic is Kendrick's, the production of the show is from Kendrick team, the stage is designed after GNX, he performs way more songs and she's even used (too boost her time) as a feature on Kendrick songs that didn't initially feature sza. The biggest crowd reactions come from Kendrick songs too (Humble, DNA, Tv off, Not Like Us, BDKMV, Money Trees,...).
People are mostly going for Kendrick and Sza fans themselves have talked about how hes stealing the show.