Never mind. It's as simple as:
# qemu-img convert ZEG-2.0.0rc1.ova -O qcow2 ZEG-2.0.0rc1.qcow2
I had split open the .ova into the .vmdk and .ovf files, and then followed the wiki for vmdk migration, but I could not convert the .vmdk. For some reason, the .vmdk alone caused qemu-img to choke. Not splitting the archive allowed the conversion to work without failure.