方法一:
luduan_info[["STAKE_84X", "STAKE_84Y"]] = \
luduan_info.apply(lambda row:wgs84toutm(row["start_longitude"], row["start_latitude"]), axis=1, result_type="expand")
划重点result_type="expand"
方法二:
luduan_info["STAKE_84X"], luduan_info["STAKE_84Y"] = \
zip(*luduan_info.apply(lambda row:wgs84toutm(row["start_longitude"], row["start_latitude"]), axis=1))