The Cottagers sent a scout to the Stadium of Light on Saturday for the Portuguese top-flight clash between Benfica and Maritimo, which the Lisbon giants won 5-0.
Zivkovic, 21, set up Benfica’s second goal and completed the rout ion the 82st minute with his third league goal of the season.
Arsenal have been linked to the left-footed star for almost two years, but Fulham’s interest appears to be quite recent and could be a result of Slavisa Jokanovic winning an internal power struggle at the club.
The Serbian boss made a loan move for fellow countryman Aleksander Mitrovic in January – partly because he knew all about him from his time and contacts at former club Partizan Belgrade.
And with Zivkovic also having been schooled at Partizan, it would be no surprise to see Fulham make a move for him if they can achieve promotion to the Premier League this season.
Paul Huntington says Preston's play-off hopes this season hinge on them getting the balance right on and off the pitch.