Convert VHDx to QCOW2
qemu-img convert -O qcow2 source.vhd destination.qcow2
qemu-img convert -O qcow2 rmcgmc01.vhdx rmcgmc01.qcow2
**qemu-img convert -f vpc -O qcow2 something.vhd something.qcow2**
Convert QCOW2 to VHD
qemu-img convert -f qcow2 -O vpc image.qcow2 image.vpc
or
qemu-img convert -f qcow2 -O vhd vmdisk.qcow2 vmdisk.vhd