Of course. Using a travel day for this stretch only won’t be worthwile though (calculate the cost of one travel day, vs price of a normal ticket).

Interrail/Eurail validity works by company, not routes. So you can take any NS (Dutch Railways) with your pass.

Yep, the line from Schiphol to Centraal is a national rail route (as Brendan indicated above) and is covered.  If it was a metro link from the airport then it wouldn’t be covered.

Excuse me eurail pass Can be made by zaandam to Schiphol airport ？