[2] He decided to try out the sport at age 16, joining the Munich Cowboys and playing two seasons for their under-19 squad as a tight end and wide receiver.
[5] In his first year, he was named all-conference at left tackle and helped the Cougars compile a record of 10–0 while being the champions of the SCFA National Division, Northern League.
[8] He repeated as a all-conference left tackle and helped the Cougars win a second straight SCFA National Division, Northern League title.
[7] After going unselected in the 2023 NFL draft, Zierer signed with the Houston Texans as an undrafted free agent.
[12] Although he performed well in training camp for the Texans, he suffered a sprained ankle in preseason and was placed on season-ending injured reserve on August 24, 2023.