Quantum interference (QI) plays a crucial role in determining the charge transport in molecular devices. In this work, the efficient modulation of QI in meta-phenylene ethylene oligomer molecular devices by a double N-substitution strategy is demonstrated. By altering the positions of two N atoms in the central ring with respect to the connecting sites, the molecular conductance can be tuned by more than one order of magnitude. Theoretical analysis, including magic ratio theory, orbital rule, and transmission simulations, reveals how the two N atoms synergistically modulate the molecule conductance between destructive QI and constructive QI states. Remarkably, addition of a second N atom does not simple reinforce the effect of the first; in contrast, it may completely cancel the effect of the first. Understanding the complex electronic interplay between the two N atoms in double N-substituted molecules paves a path toward utilization of heterocyclic aromatic hydrocarbons in molecular electronics.