Reversing course after a storm of criticism, President Miloš Zeman said on Friday that he had decided not to attend a military parade in Moscow on May 9 after all. Other European Union leaders are boycotting the parade, which commemorates the end of World War II in Europe 70 years ago, because of Russia’s annexation of Crimea and its involvement in the conflict in Ukraine. Mr. Zeman announced on Friday that he would take part in other commemorative events in the Russian capital but would skip the parade.