What should be the relationship between the output impedance of the sensor and input impedance of the MAX1464? How are they affecting each other?

The input stage of the MAX1464 is the switched capacitor. That is, during ADC sampling, the current flows into the ADC input terminals in periodic charge packets. In effect, at the beginning of each sample interval, the input impedance starts out small (large current flows into the caps) and, at the end of each sample interval, the input impedance is very large (capacitors are almost fully charged and zero current flows). This can be achieved by choosing proper filtering elements (RC-filter) on INM-INP, or by reducing the ADC clock rate.