We study manifestations of the two mechanisms of lasing without inversion i
n the nonlinear dynamics of an inversionless double-Lambda scheme laser. We
show that either of the two mechanisms can provide only continuous wave la
sing whereas their coexistence and interplay cause both a Hopf bifurcation
of the non-lasing regime and an instability of the continuous wave oscillat
ion leading to multifarious nonlinear dynamics of such a laser.