The hosts looked set to end their barren spell - neither side have managed a league victory since October 25 - when Alessandro Matri headed home 11 minutes from time.
But Samp, managed by former Roma favourite Vincenzo Montella, took their first point under their new coach as Zukanovic's set-piece on 93 minutes earned a 1-1 draw.
The result left Lazio 12th in the table, and Sampdoria - who had lost four in a row leading up to this game - just three points clear of the relegation zone.
