I don't know whether I get the correct file to look for such information.
I use this file, "S1901 INCOME IN THE PAST 12 MONTHS".
Me personally? I just use the ZCTAs a zip codes.
How about Table B19013, Median Household Income in the Last 12 Months censusreporter.org/.../
An additional quick question: what will you do to derive the information from ZCTA to zipcode level information? Many thanks in advance!