They have not yet been seen interacting in game. However, it is made clear in both of their stories and voicelines that they are familiar with one another and have several connections with each other. Ei and Zhongli have known each other since the aftermath of the Archon War. Two are both Gods, with Ei being the God of Electro/Eternity, and Zhongli being the God of Geo/Contracts.
Both of them also share some similarities. They're both quiet, timid, and don't really interact with other characters (unless they need to) besides the Traveler or only to their closest friends in the Archon Quests, Yae Miko and Tartaglia. Both of them are also known to be one of the most powerful Archons than the Anemo Archon, Venti, because of doing their duty to protect their respective regions instead of leaving their responsibilities behind. Which gives them more power and strength. Both also lost some friends across the Archon War and it made a big impact on both of them.
In the 2.1 Update, Zhongli's voicelines about Ei ('Baal' in the descriptor), he states that she would give up everyone for her beliefs, and ponders that this might be the very reason where she stands today. He also adds that should a chance come by him, he'd like to learn the Eternity she endeavors.
In Ei's voice line about Zhongli ('Morax' in the descriptor), she reveals that she had an opportunity to feast with him once, back when she was a kagemusha attending with her late sister, Makoto, during their victory after the Archon War. Informed by the traveler of Zhongli's retirement from his Archon position, she notes that he had made his choice, but she thinks that his story isn't anywhere finished yet.
In 'The Fond Farewell' quest, Zhongli's tells the traveler that the neighboring nation Inazuma, might be closed, when asked who rules the nation, he states that the Electro Archon rules the place. He notes how he and her goes by other names among the locals of their respective nations in Liyue and Inazuma, he is referred to as 'Rex Lapis', and she is 'Raiden Shogun', since she is the Shogun of the Inazuma Bakufu, he also informs the traveler that she began promulgating the 'Vision Hunt Decree', an order to seize all Visions within Inazuma's borders. He also notes that she became 'stricter' now that Rex Lapis 'has passed away', strengthening her resolve to pursue Eternity.
- “Time tempers all volition. Yet she would give up everyone for her beliefs. Perhaps it is for this very reason that she has come to where she stands today... Should the chance come by me, I too would like to learn of the Eternity for which she so earnestly endeavors.”
- — Zhongli's voiceline about Ei
- “I had an opportunity to feast with him once, back when I was just a kagemusha attending a gathering of the gods. So he's made his choice. Be that as it may, I don't believe his story is anywhere near finished yet.”
- — Ei's voiceline about Morax
As both are fellow Archons, the ship has gained some slow-rise in following, mainly on Twitter. ZhongBaal mostly portraits a fluffy or angst relationship in most fan arts due to their respective backstories. It's one of the fandom's rarepair ships. Although, some fans consider this ship as a friendship along with Venti or just see them as fellow Archons. It’s main rival ships are YaeBaal, SaraBaal, ChiLi and ZhongTao.
As of the current banner reveal events, some of the fandom noticed appearance-wise similarities (Her being a Geo Vision and polearm wielder, as well as the purple dark hair) with Geo character Yun Jin, which the fandom jokingly refer her as the 'love child' between the two.
- Both had their own banner.
- Both can make their hair glow in combat.
- Both uses a polearm as a weapon of choice.