In this work, some general forms for forced and damped complex Duffing oscillators (FDCDOs), including two different models, which are known as the oscillator (I) (FDCDO (I)) FDCDO (II), investigated by using effective analytical numerical approaches. For approximation, models of FDCDOs reduced to decoupled standard (FDDOs). After that, both ansatz method Krylov–Bogoliubov–Mitropolsky (KBM) app...