Hi, Thomas.
I'm assuming you're talking about the resistors and capacitors on Figure 34 of the AD7606 datasheet. This merely shows the analog input circuitry which is internal to the ADC. The capacitor after the switch represents the track and hold circuitry which accurately samples respective inputs.
The 0 ohms and DNI capacitors on the evaluation board are place holders for filtering or for when you need a series resistor to limit the current when your inputs are above ±16.5V.
Hope this clears it up.
Regards,
Karen