  An improved effective vector-boson approximation is applied to hadron-hadron
collisions. I include an approximative treatment and compare with a complete
perturbative calculation for the specific example of $ZZ$ production. The
results are also compared with existing approaches. The effective vector-boson
approximation in this form is accurate enough to reproduce the complete
calculation within 10%. This is true even far away from a possible Higgs boson
resonance where the transverse intermediate vector-bosons give the dominant
contribution.
