seems you need to re-init download mode before any additional heimdall commands. many times I tried to download-pit after failing to flash, and got ERROR: Protocol initialisation failed!
but after turning it off, holding volume down, and holding power-on for about 10 seconds or so, I got the Downloading... screen again, entered sudo heimdall download-pit --output /tmp/vz.pit --verbose --no-reboot, and it worked. it's a binary file, but less will show you enough of what you need to see. print-pit would have probably worked as well.
now I'm trying to reinstall the factory ROM using information here.
last updated 2016-04-25 23:36:27. served from tektonic.jcomeau.com