1.i mean madara wasn't able to break edo tensi while kabuto was controlling him but he was able to edo himself when edo tensi was canceled by itachi ,as when the user of edo tensi cancel it ,every edo one can control him self for a moment not only madar but dan was able to control himself and went to tusonade with his justu and madara as dan but he made the best use of that and edo himself as he know the edo tensi seals
2.itachi: it was just a chance as shisui's eye was programmed to get out from naruto to perform KA (save konoha)on the first one who use itachi's ms(sasuke)but itachi used his ms first before sasuke open itachis's ms so KA was performed on itachi(the first one to use his ms)
and the KA ordered itachi to save konoha as KA's control stronger than edo's control so itachi became controlled with KA not edo tensi
if shisui in these situation as edo he won't able to break edo tensi
so no one can break edo tensi even madara ,shisui,itachi and the four hokages too
2.itachi: it was just a chance as shisui's eye was programmed to get out from naruto to perform KA (save konoha)on the first one who use itachi's ms(sasuke)but itachi used his ms first before sasuke open itachis's ms so KA was performed on itachi(the first one to use his ms)
and the KA ordered itachi to save konoha as KA's control stronger than edo's control so itachi became controlled with KA not edo tensi
if shisui in these situation as edo he won't able to break edo tensi
so no one can break edo tensi even madara ,shisui,itachi and the four hokages too