Using the parallel/orthogonal space method, the semi-analytical calculation of the planar two-loop three-point diagram and two rotated reduced planar two-loop three-point diagrams will be presented. The new algorithm which allows one to calculate arbitrary NNLO calculations for massive planar two-loop vertex functions in the general mass case (as they are needed for instance for the decay of the Z-boson) will be described. The numerical stability of the methods will be demonstrated.