Is the cubic matrix (the representation of ) a 3-linear map? If so, then it is a 3-tensor. I don't think there is a notion of invertibility for k-tensors, but I am not sure.
If you don't find formulas, you can try the same approach as for normal matrices: solve analytically and write the final solution in matrix form again.
I'm not sure if that works here as your problem is not linear.