As Christopher Markus and Stephen McFeely reveal on the commentary, the original idea was to have Zemo looking for “The Mind Crown” — which is the device we see put on Bucky’s head in Captain America: The Winter Soldier and the opening of Civil War.
When we first meet Daniel Bruhl’s Helmut Zemo in Captain America: Civil War, he is on the hunt for a little red book with a black star — which notably contains the phrases necessary to transform Bucky Barnes into The Winter Soldier.
It’s a rather simple MacGuffin, but early drafts included a much more complicated one.