Throughout the Egypt location, there are often zombies that come in sets of 3:
Assuming no other zombies are a concern and no plant food is used, what plant or plant combination will defeat them the quickest?
Since they come in sets of three, the Bloomerang does quite well; it hits all 3 parts of the camel and then all 3 of the zombies after breaking the screens, and it does so twice. Bloomerangs are less effective if there is another zombie in the way though, since they will only hit up to 3 zombies before returning.
I haven't gotten very far so I can't speak for the other plants, but you'll have the Bloomerang before you start seeing the camel zombies, so they're a solid early game choice. Logically speaking, any plants that penetrate or deal area of effect damage should do similarly well; the risk with these zombies is if you only damage the front they can easily overwhelm light or modest defenses.
A good attack - only option is Lightning Reed. It attacks multiple plants at once. It's pretty weak on its own but 2 of them should take care of the trio without a problem - WHILE attacking other neighboring zombies.
Also, while this isn't a straight up "attack" answer (for that see @Ben Brocka's good one, or #1 in mine), but a good combination to defeat the camel zombie is with Iceberg Lettuce + some other attack plant.
This works (and is special enough to mention as a separate answer) because when the front zombie in the camel triplet steps on an iceberg lettuce, all 3 zombies in a trio freeze!
This slows them down enough that lighter attack plants (2 pea shooters or a repeater) can handle them easily.
Imo the best against it is bloomerang with bonk choy paired with a walnut guarding it. None will pass.