I have a minimizing problem.

$$\min y$$ $$xQx'=y$$ $$0\leq x_i\leq1$$ $$Az\leq b$$ where $Q$ is diagonal and has positive diagonal integer values and $A\in\mathbb Z^{m\times n}$ and $b\in\mathbb Z^m$ are constant matrix and vector respectively while $z\in\mathbb R^n$ is variables that contain $x_1,\dots,x_t,y\in\mathbb R$ as well.

Is this problem $NP$-hard or solvable in polynomial time?