You can get an HDMI splitter, put it on the output from a DVD player and then run an HDMI cable the inside TV and one to the outside TV and show the movie on both TV's at the same time.
The headache is running the cable to the outside. On my Vegas 24.1 it required running it behind the microwave (had to remove the microwave), then down along the side of the fridge (within the framed wall), drill a hole in the wall at the bottom of the framed wall around the fridge (had to remove the lower of the two drawers under the range), then out to the outside TV via a hole already there for the outside TV power.
The DVD player on the dash radio in the Vegas only shows on the dash screen and has low def RCA plugs that are not run to any of the TV's in the Vegas...they are just laying in the dash.
Sheree & Michael NCNG LTC(ret) with Munpi and Sheba (cat).
2016 Vegas 24.1 E350 5 speed "Ms. Enterprise", Bug-Guard Screen, Recliners, Infotainment Center, HUD, ARC Shower Rod, Safe-T-Plus, Curt SpareTire Mount,Tornado Black Tank Rinser, ext. WiFi Antenna, Roadmaster Tow Sys& Invisibrake.