When a system (working fluid) undergoes a cycle, the work output is maximized if the process is executed reversibly between two specified end states. W(1-2) is the work done when the process is executed from state 1 to 2 and W(2-1) when the process is executed from 2 to 1. W(2-1) would reach the maximum value (i.e., W1-2), if 2 to 1 is executed reversibly without any traces on the path followed. The net work done will then be zero for this cycle.
Moreover, Net work done is equal to the product of Pressure (P) and change in Volume(dV) .
Cyclic integral of any property is zero, so for a cycle , cyclic integral of P and cyclic integral of V are zero. Hence Net work done is zero.
But considering the energy dissipated in a complete cycle. The net work done might not be zero because the energy supplied might not be equal to internal energy of the system. The idea of zero work done might not be practicable and the system is not a reversible adiabatic.