Lay Waste is very strong at farming minions and harassing enemy champions.
Ask your allies to help point out when you should use Requiem to get kills in different lanes.
Picking up goo chunks is very important to staying alive.
When Cell Division is ready, try to die in a position that makes it difficult for the enemy team to kill your bloblets.
Charging Elastic Slingshot from the fog of war will give opponents less time to react.
The Karthus Zac synergy stats shown here demonstrate the areas of his gameplay that do better (or worse) when paired with Zac, compared to his overall stats. Significant differences are areas of focus that highlight how his gameplay changes when paired with this other champion.
Overall, Karthus sees a very large drop in his KDA (ratio of kills and assists to deaths) when paired with Zac. His KDA went down from NaN to NaN. This worsening shows that Zac helps Karthus perform worse in ranked League of Legends rounds. Yet, the small difference demonstrates that this performance change is only marginal.
When Karthus is an ally to Zac, he observes a small increase in his complete damage dealt. This could signal that Zac supports by providing protection for him to dish out more damage or that his support also helps extend the game's duration. Similarly, when Karthus is played with Zac on the same side, he usually scores many fewer killing sprees compared to when he plays alone. This is contrasting evidence that he is worse when playing synergisticly with Zac.
Additionally, when Karthus plays with Zac on the same side, he usually takes less damage than when he plays alone. Taking not as much damage could indicate that Zac does a decent job of protecting Karthus in team fights.
There is no universally accepted best ally for Karthus that will no matter what be his ideal teammate. Yet, overall, Zac is a superb teammate for Karthus. By playing on the same team as Karthus, he raises their win rate by 3.4% to 50.7%. This proves that there is a very strong bond between Karthus and Zac that allows them to perform at the top of their game together than alone.
Zac has a greater difficulty than Karthus. That means you need to be cautious when enlisting Zac teammates to fight alongside, as they will need a greater level of skill to fight well with you.
When playing on the same side, you should observe an overall large increase in your team’s capability to deal magical damage. Combined, these two can deal quite a lot of AP type damage.
Although, by bringing Karthus and Zac together, you probably will not be granting your team enough attack damage. Plan to bring other champions on your team that nullifies this disparity in this pairing's capabilities.
Regardless of the ability of your Zac ally, you should focus on maximizing your gold income, warding to avoid ambushes, and taking down objectives. If you do this, you will do well anyway.
To learn all of the intricacies of Karthus in order to synergize with Zac during both the lane and mid / late game phases of LoL games, you should keep reading to learn some more tips and tricks for this champion pairing. If you pay attention to the build and stats displayed above, you will increase your win rate by a lot.
The most crucial finished items to get in your Karthus and Zac synergy build consist of Rabadon's Deathcap, Malignance, and Shadowflame. When Karthus used at least these three pieces in his build, he did significantly better as an ally of Zac than with many other commonly used builds. In fact, Karthus had an average win rate of 50.7% helping carry Zac with these items in his kit.
To have the best chance of beating your oponents, you should take the Dark Harvest, Cheap Shot, Eyeball Collection, Ultimate Hunter, Presence of Mind, and Last Stand runes from the Domination and Precision rune sets. Of all the runes players chose for this champion pairing, this mix of runes resulted in the top win rate. Notably, these runes gave a 50.7% winrate overall.
If you would like to view Karthus with Zac synergy tips and builds for a a distinct rank, feel free to select one from the selection menu provided above. If viewing for the first time, the statistics and strategies shown are calculated using every round finished with both champs.