  The first measurements of the coherence factors (R_Kpipi0 and R_K3pi) and the
average strong-phase differences (delta_D^Kpipi0 and delta_D^K3pi) for
D0->K-pi+pi0 and D0->K-pi+pi+pi- are presented. These parameters can be used to
improve the determination of the unitarity triangle angle gamma in B^- -> DK^-
decays, where D is a D^0 or Dbar^0 meson decaying to the same final state. The
measurements are made using quantum-correlated, fully-reconstructed D^0Dbar^0
pairs produced in e+e- collisions at the psi(3770) resonance. The measured
values are: R_Kpipi0=0.84+/-0.07, delta_D^Kpipi0=(227+14-17) deg,
$R_K3pi=0.33+0.20-0.23, and delta_D^K3pi=(114+26-23) deg. These results
indicate significant coherence in the decay D0->K-pi+pi0, whereas lower
coherence is observed in the decay D0->K-pi+pi+pi-. The analysis also results
in a small improvement in the knowledge of other D-meson parameters, in
particular the strong-phase difference for D0->K-pi+, delta_D^Kpi, and the
mixing parameter, y.
