I have a sparse optimization problem of the form: $$\min_x c^T x + \| D x\|^2_2 + \| V x\|^2_2 - \| W x\|^2_2$$ $D$ is diagonal and $V$, $W$ are non-square matrices. I know that: $$Q = D^2 + V V^T - WW^T \succ 0$$ is positive definite. Ensuring convexity of the problem, but optimizing with dense matrix $Q$ is very slow. Can we rewrite this problem so that it is accepted by a DCP solver like CVXPY, while keeping sparse structure of the problem ? PS: problem also includes some constraints, so is non-quadratic