The ethernet library for Wiznet W5100 appears to be written to support either the AVR series or the Due. As it is, the code treats the Zero like a Due, but the SPI library is missing the function: `void beginTransaction(uint8_t pin, SPISettings settings);` I'm not sure how best to approach this for Zero. It may require changes to SPI, Ethernet or both. See: http://forum.arduino.cc/index.php?topic=331074.0