I don't think that the ACS collects asset / liability / balance sheet data. The Federal Reserve has a survey that is conducted every 3 years but it only has data at the region or census division geographies. Survey of Consumer Finances. https://www.federalreserve.gov/econres/scfindex.htm
You can build a statistical model and then use "Small Area Estimation" to get an estimate at the ZCTA geography by combing ACF and ACS data tables.
Dave Dorer