Passengers flying out of Airside 2 can get to Airside 4 without re-clearing security. Airside 2 is on the east side of the airport, where Southwest and JetBlue operate from. Airside 4 (Delta) is to the immediate south of Airside 2.

These two airsides share the same security checkpoint, so you just don't leave security when going between the two shuttles (the East Checkpoint is for Airsides 2 and 4 only - major carriers here are DL, WN, FL, B6, BA, VS; the west checkpoint is only for Airsides 1/3 - major carriers are UA, US, NW, CO, AA, AC). If they're flying out of Airside 2 but want to go to the CRC, do the following:

(1) Clear security at the East Checkpoint.
(2) After clearing security, go to the right and take the tram to Airside 4/Gates 60-99 and board the tram.
(3) Upon exiting the tram, bear to the left, towards Gates 70-79. On the left, there is a bank of elevators - one goes up to the Crown Room, the other to Gates 60-69. Take the CRC one...
(4) Exit the club, get on the tram, ride to the main terminal.
(5) Bear to the right getting off the train. Do not exit security. Get on the Airside 2 (Gates 100-120) tram.
(6) Ride tram, go to departure gate.

I did this transfer back in January - took 5-7 minutes. It's a 2 minute tram ride and a minute walk between trams. It's not that difficult.