Assuming that ze1.Nome is already a cell array, all you need to do is to replace the round brackets used for indexing it with curly brackets. This then assigns the string to the contents of a cell, rather than trying to convert the string to a cell. Like this:
ze1.Nome{end+1} = input('Introduza o seu nome: ', 's');
and the same for the other fields.
You should also consider changing the way you store the data. Instead of having a scalar struct with a cell array stored at each field, you could have a struct array with a string stored at each field. Then the line above would be
ze1(end+1).Nome = input('Introduza o seu nome: ', 's');
which may simplify some later processing. However, there will need to be changes earlier in the program to set the array up consistently with this.
