The microphone input impedance should be very high. And the line-in input impedance should also be high, but probably not as high.

I don't know exact numbers, but I wonder why you ask. What is the application which causes this question to be asked? More than likely the input impedance isn't very important, but it's hard to be sure without knowing the application.

From what I can gather, the line-out output impedance is somewhere between 0.75 ohms to 1.5 ohms depending on who you ask and how the test is performed.

The line-in input resistance is somewhere between 3000 and 4200 ohms according to the AK5572 datasheet. Input impedance is... well I don't know. High. More than the input resistance certainly. It's called "Hi-z" for a reason. High enough that it is probably immaterial to most. High, but probably less than the input impedance of the mic-in (below). So probably somewhere between 4200 ohms and 60000 ohms. I know that is a huge range, but I would expect it to be closer towards the 60000 ohm side vs the 4200 ohm side.

Mic-in input impedance: 60000 ohms according to the CS5346 datasheet.

tigerdognew
Wouldn't the input impedance also be influenced by any components between the input jack and the AK5572?

Yes, but I suspect that there isn't much.

You could try contacting EVGA directly and see if they can provide a definite answer.