Just saw this run from EWR-MAD for $424 with UA nonstop to MAD and LX with a stop in Zurich returning. Will give you a full day on the ground in Madrid
https://www.google.com/flights/#flt=...313*.USD.42313
Earlier saw the last weekend in November ( which is when I could go ) pricing at $430 but appears that’s gone. Hope this helps someone.