If hand baggage only, and the flight is on time, you should be able to make it. That said, you'll need to keep moving quickly and have almost no contingency for delays. You have to clear immigration in T4S, transfer to T4 via a people mover, and then potentially have a long walk in T4 to reach your outbound gate, particularly if departing on a Nostrum regional jet. Gates for the latter are located at the very end of the T4 terminal, via apron walkway, not airbridge.

From Iberia:
[...] the entire process requires a time of between 20 and 30 minutes, so we recommend you don’t linger in the transit area. [...]

http://www.iberia.com/us/fly-with-ib...d/?language=en

What's your appetite for risk, and what's your back-up plan if your inbound is late?