Here's a guide I've made to help beat the Pyramid of Doom in PvZ2. I'll post guides to the other Challenge Zones when I play them enough to develop good strategies for them. If you have any questions or comments, post them in the comments section, obviously.

Here is a link to my Dead Man's Booty guide.

This is a guide to the later levels, like 30+ and even as high as 50+, not the early levels. You can adapt this strategy for use in the early levels if you want to however.

Also, it works best if you've unlocked all plants you can for Pyramid of Doom, so you will always get a choice of bonus starting Sun.

Strategy 1: Normal Levels

The plants

So, here is a list of the plants you'll need:

The zombies

A list of the more dangerous zombies, and some good ways to fend them off while you are still building up your defenses.

Buckethead Mummy

This can actually be the third zombie that shows up, and they will appear in large numbers before even the first flag. Chili Beans, Winter Melons, or some Beans with a Infi-nut are the best ways to deal with them.

Tomb Raiser Zombie

This guy is a pain when he summons more graves, but there isn't much you can do about him until you have a few Beans or a Winter Melon, as Iceberg Lettuces are better saved for tougher zombies.

Explorer Zombie

This guy will wreck your defenses easily if you give him the chance. Use an Iceberg Lettuce if there are defenses in that row, or a Bean can suffice too. One Winter Melon does the trick too. Don't use Chili Beans, they're useless while the torch is lit. If the worst comes to the worst, use a Power-up to deal with him, and all the other zombies that are around while you're at it.

Pharaoh Zombie

The biggest threat, this guy is immune to Chili Beans while the Sarcophagus is intact, and other instant-kills simply destroy the Sarcophagus. A Winter Melon and Infi-nut with a couple of Beans or just a few Beans and a Infi-nut are the only good ways to deal with him early on, unless you want to use a Power-up to make it easier.

The actual strategy

Start off with a Twin Sunflower as soon as you can afford it, and use one Plant Food on it. Continue to build your economy, bust graves and kill off the early zombies with instants. One column of Twin Sunflowers will be enough, but two columns can be much better, just dig them up to replace with Winter Melons later. Hold off the early zombies WITHOUT spending any more Plant Food, unless you're maxed out and a zombie drops additional Plant Food, then spend it on your economy (Note: If a zombie is getting through your defenses and you get spare Plant Food, don't be afraid to use it to kill the zombie instead). Get two Winter Melons by the first flag in any level (they should be placed in the second and fourth rows, in the second column), along with three to five Infi-nuts.

For one flag levels, fill the third and fourth columns with Beans, and the fifth with Infi-nuts.

For two flag levels, do the same but dig up the second column of Twin Sunflowers for more Winter Melons.

For three and four flag levels, go for three columns of Beans, not two. If you have spare sun, dig up your remaining Twin Sunflowers for more Beans.

This strategy can survive using only one Plant Food per level up to level 35 (and probably beyond, that's just the level I reached before a lag-induced death, before that I still had all Lawnmowers), but some levels may require a second use of Plant Food (on economy or offense, not defense), especially if there are Pharaohs.

Strategy 2: Vs. Mummified Gargantuars

Gargantuars are so tough, you will need an altered strategy for fighting them.

The plants

The Gargantuars

Ugh, Gargs are NASTY. At least in DMB, you can insta-kill them with Spring Beans. There's no such luck here. For early Gargs, use a Winter Melon and Melon-pult, and try to stall with Infi-nuts, Twin Sunflowers and of course, Spikerocks. To save sun, dig up the plant when it's about to die, because the Garg will still smash but you can get a sun refund from doing so. Make sure to try and hit a minimum of two Gargs per Cherry Bomb, unless you HAVE to use a Cherry to finish a Garg. Also, when you have spare Plant Food, plant a Spikerock at the far right, and then use Plant Food on it if a high-health Garg is too close to your Melon-pults and Twins.

The actual strategy

You start off with a Twin in the second or third column, and use Plant Food on it. Use an additional Plant Food for each flag, or if you have Power Lilies, use all of your Plant Food. Bust the leftmost graves when you can, and stall the first few zombies with Infi-nuts, if possible. Fill the second and third columns with Twin Sunflowers, and fill the first column with Winter Melons. Afterwards, get a THIRD column of Twin Sunflowers, and in front of that, get Melon-pults.

Once you have spare sun, and a full column of Melon-pults, dig up the frontmost column of Twins to replace with Melons (starting with the top and bottom rows, they're the hardest rows to defend against Gargs), and when an Imp lands on a Twin, dig it up to replace with a Spikerock. The final setup should have one column of Winters, one column of Twins (if you have enough spare sun, dig up the top and bottom for two more Melon-pults), two columns of Melons.

Constantly use stalling tactics when Gargs are too close to the Melon-pults, and use Cherry Bombs on dense dangerous groups.

Contrary to common belief, the Tomb Raiser plus Garg combo is actually more beneficial than harmful, as you can use Grave Busters as free cannon fodder. The deadliest combo is the Explorer plus Garg combo, as Explorers force you to get Winter Melons earlier than normal as you can't stall them with Infi-nuts. By doing this, your stalling tactics are nearly useless and you have less time to prepare for Gargs. Don't be surprised if you need to use Power Ups or buy Plant Food.

Strategy 3: Premium Strategy

If you have Power Lily, you can afford to use a strategy similar to the Garg one in non-Garg levels. It makes things a little easier, but will often require Plant Food farming.

The plants

The actual strategy

It's pretty much the same as the Garg strategy, but you don't need to get Twins in the fourth column (columns two and three will be enough) and you can use Icebergs to help stall certain zombies (like Explorers, yay!). Also, you don't need Spikerocks and you won't always use Cherry Bombs.

Plant Food farming

During the Final Wave if you don't have max Plant Food, try to stall one zombie using Infi-nuts, ideally by killing off most of the weaker ones and then digging up your attacking plants. Using Cherry Bombs, you can then deal with certain crowds, leaving even fewer zombies behind. You could also try using the back zombies in groups of Camel Zombies as your stalling targets, as they are usually the last zombies to come onscreen. Pharaohs are good choices too, if you bomb a group of zombies with one Pharaoh in, that one will survive and will be perfect for stalling.