Too easy 🤭
There seems to be a certain group of people in the community that have this idea in their heads that Zatanna is a good character, and somebody needs to teach you guys why that is not the case. I don't want you guys to fall victim to misinformation.
Let's go over everything you need to know about Zatanna. First there's her stats. 900 base Damage, 1150 base Health. Already, we are off to a rough start, with not only less Damage than Health, but 250 less. But sometimes a character can be so good in every other area that it can make this not matter so much, so we must keep going and not stop there.
Her SP1 is 1 hit, chains from The Master's Death Cart, and has reduced damage due to Burning DOT attached to it. It also has a meterburn minigame, making it very slow to complete compared to all the other minigames. It only applies 1 gear effect from gears like Claw of Horus and DOT gears (Ibistick, LexCorp Helmet, LoA Blade). Not ideal for the purpose of a SP1 carry, and not very remarkable for the purpose of a support. I will however point out that this is the only SP1 in the game that is both ranged, so it chains from death cart, and applies Burning DOT, all other SP1s (Scorpions) that naturally apply Burning DOT are not ranged. Burning also applies power dampening to the opponent, and this can stack with additional applications of Burning DOT to make the opponent have very low power generation, meaning that her SP1 does have some synergy with LexCorp Helmet and The Ibistick. Although if you are looking for a SP1 that nerfs the opponent's power generation, you will never find a better one than Killer Frost Prime or Regime Killer Frost's SP1s, as they apply Deep Freeze, which is not only a stronger version of power dampening, but a means of slowing the opponent down to a snail's pace so that it is extremely easy to attack them while they attempt to hit you with super slow basics.
Her SP2 is very different from any other in the game. It has you pick from a variety of buffs or de-buffs each time you use it. Some of these are helpful, like damage increase (this will go away if you tag out), or power drain, maybe the healing card in some cases, others are not very helpful, like the DOT card (very small amount) or the Joker card which can make you stun yourself. This is technically the Minigame of the special. Because her SP2 has no traditional minigame attached to it, she does not get a damage increase modifier for completing it like you normally would. Almost all specials have a minimum and a maximum amount of damage they can deal to an opponent, and this number is determined by the % score you get on the minigame. If you don't complete the minigame at all, it will not get a damage increase. If you do, you will get a damage increase based on how you scored. Zatanna's SP2 operates as if you always failed to complete the minigame, which means the SP2 is very weak. Not to mention that because it has a lot of hits on it, the damage that each individual SP2 hit will deal will be low, as the damage is divided many times across its many hits. This means the SP2 is absolutely not ideal for bypassing health threshold effects and passives such as Astro-Harness users, Prime Ravens (her passive will slow time for a second and cause the remainder of the SP2 hits to fizzle out, so it won't continue hurting her after the health swap occurs), John Stewart teams, or New 52 Shazams. It will also not ever be KOing Red Son teams utilizing Red Son Green Lantern, or crit immune AK Batman, because she HEAVILY relies on getting critical hits, more than other carrys, and without them she will hit like a wet paper bag.
The one good thing that I can say about her SP2 is that it's one of the few in the game that can apply gear DOT many times in a single special. If using LexCorp Helmet, The Ibistick, or League of Assassins Adept Blade, her SP2 can apply DOT from these gears, and it can even apply them after you do a full heavy combo to knock the opponent down. The SP2 will not connect, but the DOT will still apply. If using Tantu Totem, you will get Power Refund while still having applied the DOT on the opponent, meaning you get your power back to be able to use another SP2. Notably Static and Jessica Cruz (the other SP2s that apply gear DOT) cannot do this, because their SP2s are too long to give you power refund when attempting to use one after a heavy combo. This could be neat for Survivor, in the fights when SP2s are allowed, or maybe for completing Phantom Zone DOT objectives. But Aquaman Prime will always be better for the role of a gimmicky DOT applier, especially as you are much easier completing more objectives than just DOT, such as Tag-ins and Specials used. One of the biggest roadblocks for this strategy is Blackest Night The Flash used on a full Blackest Night team, and in that instance she is completely and utterly screwed. Her SP2 will be too weak to KO the opponents through all of their health bars, and the DOT applied from her SP2 will feed them health and power extremely fast, turning them into her worst nightmare. In Aquaman's case, at least you can (and should) pair him with The Batman Who Laughs so that you can KO the Blackest Night characters with Savage Robin tag-in damage.
So let's review everything we've talked about here. We have some bad stats, an OK SP1 for a support, a gimmicky SP2 that's very bad for a carry but can be good for Survivor or PZ, although still outclassed by others in that regard.
In my most honest opinion, I can confidently tell you that this is not a good character. I do not recommend using her, and you do not have to complete her challenge. The only thing you would get out of her challenge that could be beneficial is perhaps a first ever copy of her if you don't own her yet, so that if you ever pulled her from a pack opening or from a Phantom Zone reward in the future, you would have the option to then sell her.