whether in memory or surgery, ballet or computer programming

【答】在whether...or... 之间，无须使用完整的句子，目的是省略原来可能重复的成分。这种用法太常见了。又如：

Do the work well whehter by yourself or with the help of others.

如果说成下面的句子，就太啰嗦了，简直是累赘：

Do the work well whehter you do it by yourself or you do it with the help of others.

网友的句子，也可以补充完整，照样啰嗦，累赘极了：

Or, put another way, expert performers—whether they are expert performers in memory or they are expert performers in surgery, （whether）they are expert performers in ballet or they are expert performers in computer programming—are nearly always made, not born.