LAS VEGAS—Nevada’s first execution in nearly 16 years is on hold again after the state’s lawyers told a federal judge on Monday they couldn’t possibly satisfy the legal requirements necessary to put Zane Michael Floyd to death before April. “It would be impossible,” Randall Gilmer, chief deputy Nevada attorney general, told U.S. District Judge Richard Boulware II. Gilmer said during the brief hearing Monday that Clark County prosecutors have not obtained a formal death warrant necessary to execute him by lethal injection before one of the drugs the state plans to use expires on Feb. 28. Boulware scheduled a status hearing for April 5. Floyd, 46, was convicted in 2000 of killing four people and wounding a fifth in a shotgun attack at a Las Vegas grocery store. The state’s lawyers requested Monday that Boulware go ahead and rule on evidence both sides presented late last year about whether the …