  We theoretically investigate the microwave-active resonance modes of a
skyrmion crystal on a thin-plate specimen under application of an external
magnetic field that is inclined from the perpendicular direction to the
skyrmion plane. In addition to the well-known breathing mode and two rotation
modes, we find novel resonance modes that can be regarded as combinations of
the breathing and rotation modes. Motivated by the previous theoretical work of
Wang $et$ $al.$ [Phys. Rev. B {\bf 92}, 020403(R) (2015).], which demonstrated
skyrmion propagation driven by breathing-mode excitation under an inclined
magnetic field, we investigate the propagation of a skyrmion crystal driven by
these resonance modes using micromagnetic simulations. We find that the
direction and velocity of the propagation vary depending on the excited mode.
In addition, it is found that a mode with a dominant counterclockwise-rotation
component drives much faster propagation of the skyrmion crystal than the
previously studied breathing mode. Our findings enable us to perform efficient
manipulation of skyrmions in nanometer-scale devices or in magnetic materials
with strong uniaxial magnetic anisotropy such as GaV$_4$S$_4$ and
GaV$_4$Se$_4$, using microwave irradiation.
