What's your code?
Just straight from the example pretty much
class ZipStream : public sf::InputStream
{
public:
ZipStream(string archive);
bool openFile(string archive);
bool open(string filename);
sf::Int64 read(void* data, sf::Int64 size);
sf::Int64 seek(sf::Int64 position);
sf::Int64 tell();
sf::Int64 getSize();
};
And then I call it from my main cpp file with
ZipStream stream("data.zip");