Zoo Lights is pretty fun. The new light show this year was nice, and I even saw a few animals out lurking, which is a good switch up from my prior, animal-devoid visits, which make me wonder why I am at the zoo to begin with. This year they are offering camel rides, which is a fun new addition.
You can also continue to pay an arm and a leg (okay, only $3) for a churro, a Christmas tradition I have enjoyed for many years.
My ultimate suggestion- go, but go around 8 pm. That's when all the parents and kids start to leave, parking opens up, and it's generally less crowded.