Hi Eric,
CLS. Yes 0 is a valid CLS score and is taken into account. CLS is reported at the end of the page rather than by each shift. In effect the score is updated with each shift. If there was no update, then the original initial value of 0 is reported.
INP depends on interaction. If a user visits a page and doesn't perform any interactions on the page (note that scrolling with the scrollbar or mouse does not count as an interaction), then the INP value is N/A and it NOT included. INP is only a measure of page views with interactions. And INP of N/A is expected for many static pages and is not an issue. It will not prevent the page from passing Core Web Vitals in tools like PageSpeed Insights. Where pages have "no-op" interactions (e.g. clicking on a random place on the page which has no event handler) it will likely have a small time > 0ms anyway. So an INP of 0 is pretty much technically impossible.
LCP is only included when reported. There are some pages with no LCP-eligble elements (e.g. just a big canvas, or content animated onto the page). In this case no LCP is reported and it is not taken into account (LCP is NOT 0 in this case and is more like N/A). This is extremely rare and the vast majority of pages have an LCP element and are included.
Hope that helps,
Barry