Five years ago, a TV personality and comedian, Volodymyr Zelensky, won the presidency in Ukraine in a landslide victory. When Russia launched a full-scale invasion of the country three years later, he faced the biggest challenge of his presidency and of his life. Despite initial success beating back one of the world’s largest armies, the tide has turned against him. Andrew E. Kramer, the Kyiv bureau chief for The Times, sat down with Mr. Zelensky to discuss the war, and how it might end. Guest: Andrew E. Kramer, the Kyiv bureau chief for The New York Times.