Thats right. Flash the e-recovery onto device in the same way you did earlier. Can I ask what command you use for that? Did the given example in the install instructions work, or did you use another? It would be helpful to know. 
It’s just factory reset really, but it formats data as well. Slightly different steps to twrp but achieving the same results more or less.
- When e-recovery home screen is up and running, select Factory reset. Next select Format Data/factory reset.
Screen will go white and output at bottom left (very small letters) when done.
- Return to e-recovery home screen (if not already there, can’t remember ) and select Apply update. Next select Apply from ADB.
If device wasn’t plugged to pc, plug it in now and issue the command to sideload the OS zip.
Terminal output should now show " serving"something or other as the zip is transferred across, with a percentage amount.
It will stop at 47% (all being well) and everything is being done on device. Watch the on screen output for Step 1 and then step 2. Its quite slow and you may think nothing is happening, but wait until the recovery screen changes and you then press the back arrow at top left. Output should show install status.
Press reboot system.