Over nearly four years of wartime leadership, analysts say the Ukrainian leader has repeatedly played weak hands wisely. A U.S. peace plan may be his biggest test.It is another make-or-break moment of wartime leadership for President Volodymyr Zelensky of Ukraine. Late last week, the Trump administration delivered to Mr. Zelensky a 28-point peace plan that many Ukrainians and their Western allies have called a wish list for Russia, a reward for its aggression and a betrayal of Ukraine. The Ukrainian leader was given seven days to either accept it or potentially watch the United States walk away from any remaining...