Traffic starts building around 3 and then just keeps growing till about 7 or later for the areas you are talking about.
How long do you plan to be at the zoo? It opens at 9 a.m. and if you hope to be at the beach and eating a picnic (lunch?), you'd only get a couple of hours there. It is a huge zoo and worth spending more time than that, IMO.
As pps have said, go to the Zoo, leave at 2:30 p.m., head to La Jolla, spend a few hours there, have a picnic dinner or eat dinner somewhere in La Jolla, then head to Anaheim around 7 p.m.
Anaheim is not bad distance-wise from La Jolla, but why have it take 2 - 3 times as long because of bumper-to-bumper traffic when you can be enjoying a lovely time at the beach or dinner and then zip up without aggravation later?