Despite winning 3-1 at Anfield tonight, the Reds were dumped out of the competition after the two-legged tie finished 3-3 but Zenit's away goal on Merseyside allowed them a path through to the Round of 16.
That kicked Brendan Rodgers' side into gear and they were soon back on level ground on the night when leading scorer Luis Suarez fired a free-kick through the wall and into the back of the net in the 28th minute.
The home side then edged ahead two minutes before the break through Joe Allen who was able to hook the ball past Vyacheslav Malafeev after his initial header had been parried by the Zenit keeper.
Liverpool then made it 3-3 on aggregate just before the hour-mark when Suarez produced a sublime free-kick which he curled into the top corner.
Rodgers' side then searched for the winning goal and had a few chances to do so but Zenit held out to put themselves into the next phase where they meet Swiss club FC Basel.
2012/13 UEFA Europa League - Round of 32 second leg
Anfield, Liverpool - 43,026