|Date of birth||May 19, 1993|
|Place of birth||Lawrenceville, Georgia, United States|
|Height||6 ft 3 in (1.91 m)|
|2010–2011||United States U18||3||(0)|
|2011–2013||United States U20||10||(2)|
|2015–||United States U23||1||(0)|
* Senior club appearances and goals counted for the domestic league only and correct as of August 31, 2015.
Walker played all of his youth soccer at Gwinnett Soccer Association in Lilburn, GA. Walker was coached by several individuals but continued to develop his skills and take it to the next level with coach Nuno Piteira.
College and Amateur
Zimmerman played college soccer at Furman University between 2011 and 2012. He was named First Team All-Conference 2011, Southern Conference Freshman of the Year 2011, and National Soccer Coaches Association of America/Continental Tire NCAA Division I Men’s All-America Second Team in 2012.
FC Dallas selected Zimmerman in the first round (No. 7 overall) of the 2013 MLS SuperDraft. He made his professional debut on May 11, 2013 as a late substitute in a 2–1 victory against D.C. United.