Mills attended Urbana High School in Frederick County, Maryland from 1996 to 2000, where he led the school's football team to consecutive 2A state championships in 1998 and 1999, going undefeated both years. In the course of his high school career he broke Maryland public school records both for passing yards (5,638) and touchdown passes (59) and won countless awards including first team All-CMC and first team All-Mid-Maryland. Mills was also a standout on the basketball team.
As the quarterback of the Nittany Lions from 2001 to 2004, Mills led the team to the Capital One Bowl in the 2002 season. Mills was a three-time Davey O'Brien Award finalist and was presented with the 2004 Hall Foundation Award as Penn State's outstanding senior football player. In 2002 Mills was named All-Big Ten.
Mills holds many Penn State passing and total offense records: He finished his career with a school record 7,796 yards of total offense, 41 career touchdown passes (since broken by Daryll Clark) and subsequently Matt McGloin, and 16 career 200-yard passing games. Mills is the first Nittany Lion under head coach Joe Paterno to throw, catch, and run for a touchdown in a single game (in 2004 versus Akron). He wore jersey number 7.
Mills spent the 2005 preseason in the Washington Redskins' training camp as an undrafted free agent, but was released before the season began. He pulled his hamstring early in camp and the injury prevented Mills from participating in most drills. He wore jersey number 14.
In 2006, Mills served as an assistant coach at Temple under first-year head coach (and fellow Penn State alumnus), Al Golden. He joined the coaching staff at The Haverford School in Haverford, Pennsylvania as quarterbacks coach in 2007, leaving the team after the 2010 season.
- "Passing into history: Mills moves on from PSU career, leaves behind lasting QB legacy", Jenny Vrentas, The Digital Collegian, March 3, 2005
- "Mills' agent optimistic about NFL prospects," The Digital Collegian, March 16, 2005
- "NFL draft analysis for Zack Mills"
- "Passing into History," The Digital Collegian, March 3, 2005
- "Zack Mills Named Senior MVP At Nittany Lion Football Banquet" gopsusports.com, December 12, 2004
- PSU’s Mills enjoying retirement, The Citizens' Voice, July 20, 2007.
- Haverford School Football, haverfordpafootball.vnsports.com, January 5, 2012.