If you haven't installed any FUSE yet:
brew tap homebrew/fuse
brew install Caskroom/cask/osxfuse
brew install qemu ext4fuseqemu-img convert -p -O vmdk snapshot.qcow2 system.vmdkThis will take some time...- Download and register for a free licence of VMDK Mounter for Mac® OS X and install it.
 - Reboot your macOS device.
 - Mount the vmdk volume by double clicking it.
 - Mount the partition: 
ext4fuse "/dev/disk3s2" "/Volumes/kvm-snapshot"(you have to edit it to your disk numbers) - Now you can access it with the terminal.
 
VDMK Mounter is discontinued, I was able to mount vmdk using VirtualBox