Sounds written s and z
I consider the sound written s in words like fazes to be an allophone of the phoneme /s/, although in Portugal it nearly always sounds the same or practically the same as phoneme /S/. By considering this [S] as a fully predictable allophone of /s/, and not of /S/, it is easier to explain that:
On the other hand, one could argue that the written s in casa, which sounds as [z], is also an allophone of /s/, and not of the phoneme /z/. But although the written s predictably changes to [z] when between vowels, it doesn't mean that all sounds [s] change to [z] in that position, which is clear from words like disse and faço. For that reason I chose to count intervocalic [z] written s as part of phoneme /z/.