We present a fully time dependent, adiabatic solution, and steady-state analysis for the ultraslow propagation of the nondegenerate four-wave mixing _NDFWM_ signal and the weak probe beam in a closely-cycled double-ladder system. A Under appropriate _especially power balance_ conditions, the two-mode probe and phase-matched NDFWM pulses, after a characteristic propagation length, evolve into a pair of amplitude and group velocity matched pulses. A Double transparency for the probe and NDFWM beams can be achieved owing to an efficient one- and three-photon destructive interference involving the NDFWM beam and its back reaction to the probe beam. A The forward and backward configurations are investigated in this double-ladder system, and their efficiencies are calculated and compared.