When using the Elk inputs for analog measurements, the built in 'pull-up' resistor can seriously influence small current drive capable voltage measurements. By removing the pull up resistor, one would get a true reading from this voltage source as it now doesn't have to 'overcome' that resistor. Of course, you still get only eight bit resolution (for more info on that see my
Analog to Digital Converters Explained Guide).
Also, I believe you still have an 'update' issue on the zones themselves, especially on an expansion card.