  We study the applicability of the Z-Sum approach to multi-loop calculations
with massive particles in perturbative quantum field theory. We systematically
analyze the case of one-loop scalar integrals, which represent the building
blocks of any higher-loop calculation. We focus in particular on triangle
one-loop integrals and identify strengths and limitations of the Z-Sum
approach, extending our results to the case of one-loop box integrals when
appropriate. We conclude with the calculation of a specific physical example:
the calculation of heavy-flavor corrections to deep-inelastic-scattering
structure functions.
