“I’m un-retiring for six months,” 34-year-old Zina Kocher said with a laugh on the phone earlier this week. Kocher, who lives in Canmore, Alberta, announced via Instagram on Oct. 2 that she was returning to elite-level racing with the one-and-done hope of making the 2018 Winter Olympics in PyeongChang, South Korea. As she referenced in her social-media post, Kocher’s return to the trails will be “4k” (kilograms) lighter — her current run at the Olympics...