All three judges favoured DeGale 118-109, in what was a one-sided bout but nonetheless a solid performance from the English fighter.
A left uppercut in the third round dropped Zuniga, but after the Colombian met the count ‘Chunky’ was unable to press further for a more decisive stoppage win.
DeGale turned up the heat in the sixth but was troubled by a clean Zuniga shot in the penultimate round.
Soaking up the shot, DeGale held on for the unanimous decision for the unnecessary extra WBC belt though the ‘championship’ should at least strengthen the Brit’s charge for a legitimate world title challenge sometime in 2013.
Earlier in the evening, Chris Eubank Jnr stopped Latvia’s Olegs Fedotovs in his second fight in eight days.
The 23-year-old defeated Bradley Pryce on points one week prior on the Tyson Fury undercard, and wasted little time in ending Fedotovs in the second round to take his fledgling pro record to 9-0.
And promising 22-year-old super bantamweight Kid Galahad moved to 13-0 with a fourth-round knockout of Spain;s Ivan Ruiz Morote.
A stiff right to the head of Morote was enough to secure the win with 10 seconds remaining in the stanza.