President Volodymyr Zelensky of Ukraine said he was surprised by President Trump’s shift in position regarding Russia’s war with Ukraine and that he believed that he and Mr. Trump have a “better relation that before.”His remarks came in an interview with Fox News on Tuesday evening, after Mr. Trump said in a social media post on Truth Social that he now believed that Ukraine could, with financial support from NATO and the European Union, regain all of the territory it has lost to Russia. It was a head-spinning comment considering that only a month ago the president backed a plan to have Ukraine give up land in return for peace. Mr. Zelensky also said the seeming unwillingness by President Vladimir V. Putin of Russia to take steps toward peace had helped Mr. Zelensky’s relationship with the American president. “The fact that Putin was lying to President Trump so many times also made a difference between us,” said Mr. Zelensky, speaking with Bret Baier of Fox News. In the interview, the Ukrainian leader presented a cautious optimism about Mr. Trump’s support of Kyiv’s position in the war.