Use ogr2ogr
to convert shapefile to geojson
for f in *.shp; do ogr2ogr -f "geojson" ${f:r}.geojson $f done
npm install --save @mapbox/geojson-merge
geojson-merge *.geojson > combined.geojson
https://www.zillow.com/howto/api/neighborhood-boundaries.htm