# Fake some 3D data but with epsg:4326
gf_orig = gpd.GeoDataFrame(geometry=gpd.points_from_xy([-120.4], [48.6], [1400]), crs='EPSG:4326')
# override 4326 with 3D CRS and do a 3D transform (uses pyproj under the hood):
gf_new = gf.set_crs(epsg=7912, allow_override=True)
gf_new.to_crs(epsg="2927+5703")