Here's a guide I've made to help beat Arthur's Challenge 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 Pyramid of Doom guide.

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

Here is a link to my Terror from Tomorrow guide.

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

You also HAVE to get additional starting sun card for this strategy to work. Sun-shrooms just don't cut it for sun production in later levels, you need to start with Twins.

And lastly, with the right strategy, even Wizards can be rendered nearly harmless. That said, you may find yourself using a few power-ups in four flag Wizgarg levels, no matter how good you are at these strategies.

Strategy 1: Easy Levels

This strategy is for any level without Gargs, Wizards or Jesters.

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.

Knight Zombie

Early knights are an absolute beast if they appear in big amounts. Use stalling tactics to crowd them together and then bomb them. That is, if you haven't got a lot of melons yet.

Zombie King

What's worse than a lot of Knights? Every regular, Conehead and Buckethead zombie turning to Knights TOO. Cherry Bombs in the eighth column can take out groups of Knights and the Kings too, but otherwise, there isn't a lot you can do to take out the early Kings.

Jester Zombie

If you have these guys, use the second strategy, not this one. Freeze individuals with Iceberg Lettuces to use direct melon damage on them, or try to use splash damage to deal with them. For groups, PF-ing an Iceberg should give your Winter Melons enough time to kill them.

Wizard Zombie

STUPID STUPID STUPID SHEEPIFICATION SPELL!!! Ahem, anyway, these guys also will destroy you if you use this strategy. Using strategy 2, freeze individuals or use well-timed Iceberg PF for groups, like you would with Jesters. If they sheepify too many plants (or all of your plants), use a Cherry Bomb to clear out a group of them and turn some plants back to normal. In four-flag levels when approaching or above level 100, there is no sure way to survive them without boosts or power ups unfortunately.

The actual strategy

Start off by planting (and PF-ing) Twins in columns 1-2. Bust graves in columns 6 and 7 first, and plant Infi-nuts in column 6. You need column 7 clear to freeze zombies while they attack the Infi-nut. Plant Power Lilies whenever it's charged, and if necessary use PF on Infi-nuts, Icebergs or Twins. Or even early-charge a Cherry Bomb. Get Winter Melons in column 3, continuing to bust graves (prioritizing sun graves and graves that are nearer the house), then build up Melon-pults in columns 4-5. Once you have the full columns of melons, you should be set. Overall, it's relatively simple.

Strategy 2: Hard Levels

So, want the firepower to deal with Knight spam or Gargs but don't want Jesters to reflect your attacks? Want to stall the Gargs effectively so that you can beat infinite amounts? Want to have a strategy that is vaguely effective against Wizards? You've come to the right place!

The plants

The Gargantuars

Hey, a Challenge Zone where my anti-Garg strategy is 100% effective! I need to adapt this strategy for PoD and BBB...maybe DMB too. Anyway, with Iceberg stalling, it's rare that they'll ever get to your Infi-nuts. Honestly, the IMPS are bigger problem.

The actual strategy

Do the same as you would in strategy 1, but keep in mind that you'll need to save your Plant Food a lot more. Get Twins in columns 1, 3, and then 5, with Infi-nuts in columns 6 as before. Put an Iceberg Lettuce somewhere in column 5 instead of a Twin, and that will be your main Iceberg for freezing zombies. Get Winter Melons in column 2, aiming for a full column by the first flag, and use individual Icebergs on Jesters, Gargs or Wizards, and plant food on big groups.

Build up more melons in column 4, and then eventually dig up Twins in column 1 for more Winter Melons. If faced with Gargs, time Iceberg PF when they're either throwing an Imp, or so that an Imp will freeze when it touches the ground. When faced with Wizards, freeze them just before a group starts casting spells. With Jesters, only freeze when lots of them are deflecting your attacks.

In the event that an Imp eats a Twin in column 3, don't bother to replace it, put an Infi-nut there for defense against the Imps instead. The odds are that if you start losing Twins in column 3, then replacements won't pay for themselves before they die. You still have four Twins in column 5 after all. Use Cherries if groups of Gargs are actually going to cause major problems, or to deal with Wizards should too many plants get sheepified.

Mostly though, you need to be good at improvisation for the strategy to work, as many levels may surprise you with things such as early Wizards or Kings, Jester spam, Knight spam, and so on. Each level is unique and you can't just beat them all the same way. If you can't improvise, even the best AC strategy (which is probably this one, even if I say so myself), won't do you any good.