We investigate mixing properties of piecewise affine non-Markovian maps acting on $[0,1]^2$ or $[0,1]^3$ and preserving the Lebesgue measure, which are natural generalizations of the {\it heterochaos baker maps} introduced in [Saiki, Y., Takahasi, H., Yorke, J.A.: Nonlinearity {\bf 34} (2021) 5744--5761]. These maps are skew products over uniformly expanding or hyperbolic bases, and the fiber direction is a center in which both contracting and expanding behaviors coexist. We prove that these maps are mixing of all orders. For maps with a mostly expanding or contracting center, we establish exponential mixing for H\"older functions. Using this result, for the Dyck system originating in the theory of formal languages,we establish exponential mixing for H\"older functions with respect to its two coexisting ergodic measures of maximal entropy.
2020 Mathematics Subject Classification. Primary 37A25, 37A40; Secondary 37A55.