hellow,
my name is Zeleznik Ziga and I live in Slovenia (Slovenia was part of Yugoslavia and before that part of AustroHungerian Monarchy). First I must said that Im not looking for my relatives - I have some in USA but they are migreted with other names.
I want only explain that as I know Zeleznik is typical Slovene name, and of course if you thinking that yours ancestors were migreted in USA from Austria you are probably right - when it was happened in years before 1916. But I doubt that they are from Slovakia.
And yes, first letter Z (in name), have in original Sloven character set a corone and it is pronounced as 'zh' in 'doctor Zhivago' or 'su' in 'measure' or 'leisure'.
Good luck in your searchings!
Ziga