The interplay between toroidal rotation u, parallel flow shear u? and perpendicular flow shear ?E in the stabilisation of tokamak turbulence is investigated in non-linear flux-tube gyrokinetic simulations with the GKW code. The non-linear simulations are performed for a reference L-mode DIII-D plasma (the so-called shortfall case) at r/a = 0.8, varying the flow parameters around their nominal values. Depending on the respective signs of u, u? and ?E, turbulence is found to be enhanced, reduced or unchanged. When the coupling is favorable, the overall effect on the nonlinear heat fluxes can be very large, even at moderate flow values. The ion heat flux is for instance decreased by a factor of three when the direction of the parallel flow shear is reversed with respect to its nominal value. Even more surprising, keeping u? and ?E at their nominal values, the ion heat flux decreases by more than 50% when the toroidal flow is reversed. The relevance of this mechanism in the experiments, which depends on the ability to decouple u, u? and ?E is discussed.