I have spend about half hour finding maps of Hungarian Empire from oldest to nevest and Zakarpatia was always part of it, use google, type map of Hungarian empire and which year do you want and see for yourself, Zakarpatia was never part of Eastern Slavs, just from 1945 till nowadays. And no one exactly knows what was before that (before Hungarian Empire), thanks to poor documentation available. Some believe that was part of Great Moravia and others it was part of Kievska Rus.