Zellner attended Mary Persons High School, where he lettered in football and basketball.
In 1996, he transferred to Fort Valley State University, but eligibility problems limited his playing time to only 3 football games, collecting 18 tackles (4 for loss).
In 1997, he focused on basketball, starting at forward (17 out of 26 games), averaging 10.1 points, 9.3 rebounds and 1.4 blocked shots, while helping the school win its first conference championship since 1969.
Against the Atlanta Falcons, he posted his first career sack, while adding a quarterback pressure and 2 tackles.
He missed the last 4 games, after being placed on the injured reserve list with a torn left anterior cruciate ligament he suffered during a practice.
[6] In 2004, Zellner replaced an injured Fred Wakefield, playing in all 16 games (14 starts), while registering 35 tackles and 2 sacks.