Nana is capable of great magic and without being able to control it she was able to create a hurricane over an entire forest. Even after creating a natural catastrophe she was able to calmly walk away, which means she was able to withstand wind speeds of 250 kph and not be injured by the pieces of the "meow playground" flying around within it, which for reference, park playground sets are often 5000+ kg, making her stronger than any reasonable human just with her base stats. We can automatically place her above Vale for her capacity to withstand winds, and Vale can be assumed to equal to Valir, who is stronger than Gord. Nana being stronger than Gord means she is also stronger than Eudora while places her above mortal mages. In the end of Nana's story, she seeks out a magical fruit that will allow her complete control of her power. As seen in Aurora's story, by reaching a high level of magic she was able to obtain immortality and vast power. Nana's fruit would theoretically give her the highest level of magic power therefore making her stronger than Aurora, and by association, Zhask.
Aurora being the strongest magical entity by far places her above everyone except those from or affected by the Celestial realm, and outlanders. In her story, Molina dies, but she later is able to carry Molina with her, making the only known entity in the ML universe capable of reviving something that is already dead, making her abilities more powerful than the Twilight Orbs as Valentina was seeking them out for the same purpose of reviving the dead. As her power surpasses the Twilight Orbs, this makes her stronger than Lunox who was able to be sealed within them. This makes Nana stronger than the Lord of Light and the Lord of Abyss as Lunox has been shown to be able to control their power. The Lord of Light and Lord of Abyss have been shown to be stronger by the celestial ones as the celestial ones attempted to control them and failed. This means Nana is stronger than Edith, Kaja, and Uranus.
Leaving only outlanders, I will jump to Harith's lore very quickly. Harith was authorized to control space and time by the Moniyan Empire which through skill descriptions can be assumed to be due to his keys. In his lore, Nana is shown to be attracted to him, but she is actually only rizzing him up to have access to these keys. This means Nana is already actively trying to take over the space and time of the world and makes her stronger than Natan since she does not even need a time machine. Her lore says that she will "continue to grow" so it can be logical conclude that she will eventually succeed at her goal. Being able to time travel would give her access to the space-time rift that Yve exists within. Nana ranking above Zhask means she can be a match for Yve and they would be able to fight. Her control over space means she is also able to access similar powers to Cyclops.
It might seem impossible for Nana to rank any higher, but let me pause you there and direct you to an earlier point. The presence of the Unique God, the Greater One, who created the Land of Dawn and who Lunox holds the power of. Nana is able to use her a ranking above Lunox to rise to multiverse level threats. But, refer to Nana's story which confirms the exact type of magic Leonins use to be spiritual. Nana being the confirmed strongest magic user as she has reached peak levels of power means she also ranks above the only other spiritual magic user known- Gatotkaca. Gatotkaca's story explains that he trained inside the Cauldron of Heaven, the Candradimuka. Martis and Gatotkaca are evenly powerscaled and Gatotkaca is not once mentioned to be the strongest entity in his race, yet he has heavenly powers while Martis only "makes the heavens shake."
Consensus: With this, it can easily be concluded that Nana is stronger than both of them, making her the highest ranked threat in lore at the moment and easily the strongest being within the MLBB lore multiverse.
