download for latest release is a link at bottom of release notes pdf.
Cannot advise how to install from command line/ssh with putty.
If you have recent backup config file (I hope) then could do a factory reset and start from that.
Basic configure back onto network to get ZD GUI.
Then go through whatever firmware steps you need to get to where you were then restore backup config. Long involved process, not difficult, just many steps and time consuming.
Better to wait for bigger minds than mine to advise.
The tech support staff are very good...worth opening a case and getting some help.
I downloaded the firmware from premium user account .... and recovered the rescue mode message error "no storage connected" ....
Please see the article # 000001481
after completing this procedure try to hard reset again ....