@JeremyECrawford Can a wizard cast greenflame blade outside of a silenced area, move into a silence area, then execute the melee attack?
— John Carney (@JohnCarney) December 18, 2016
See "Moving between Attacks" (PH, 190) for how breaking up your movement works. #DnD https://t.co/XXIeBTVMrj
— Jeremy Crawford (@JeremyECrawford) December 18, 2016
Moving Between Attacks doesn’t apply here as there A not multiple attacks involved, nor is the attack action being used. The question really is “can you move in between using the Cast a Spell action, and the melee attack that is required as part of the casting of said spell?”