Sounds too specific. Zoro has a powerful soul too and conqueror's Haki, which in itself is the representation of a kingly soul. And after all, Zeus isn't itself a soul, but lightning reinforced with a strong soul, which shouldn't be different from other attacks by those with a strong soul. Especially swordsmen, whose swords too possess powerful souls, with Big Mom being concerned about Enma
Yes ofc, but can Zoro phase through Objects?
Zeus didn't just Attack, he went through S-Shark's Body
Brook can also do such thing with his Soul
There are Two Things we must understand about Lunarians
1. Their Invincibility is related to their Flames
2. There is No Way that they can keep their Flames On Permanently (There must be a Rule)
I don't want to go into Details, but here is my Explanation (You can call it Headcanon since i'm not providing my Full Arguments for now):
Lunarians's Flames is their Life Energy
Their Invincibility comes from it, however it's Temporary depending on how much they "Recharged" it
How do they Recharge it? By Disabling it. It's like those Flames have a Battery, whenever they take Damage or they simply make Lot of Effort/Fight, that Battery gets consumed more & more, so a Lunarian decides to Disable their Flames to get that Battery back to 100%
This is why King for example is always seen with his Flames-On, meaning it's 100% Charged
But while Fighting, he Disables it from time to time, even though it means putting him at Risk
This is also why he was blocking some of Zoro's Attacks even when he had Flames-On, it's cuz he didn't want that Battery to be Drained Fast
But what does Disabled Flames really mean? I believe a Lunarian can send their Flames to another Place where it gains Invincibility, so when the Flames return to them, their Bodies gain that Defense. And this was proven by Brook who explained during Fishmen Island that his Body is Powered-Up by his Special Soul, and he keeps Joking about it, he can See even though he doesn't have Eyes, he can Hear even though he doesn't have Ears & basically everything else a Human can do
Why? It's cuz his Soul kept all the Functions of Human Brook, meaning his Skeleton gained the Same Abilities that Human Brook was capable of (It's like the Soul held on to those Functions & gave them back to the Skeleton). Based on this Logic, we can conclude that Lunarian's Flames gives them Invincibility because they come from a Place/Body that is always Invincible
To Re-Phrase it better, there is a Place or Body or Power Source that has True Invincibility (Meaning it's Uncapable of taking Damage)
And Lunarians have Ability to Transfer their Flames to that Place/Body/Source so that when it returns to them, it gives them that Invincibility (Just like Brook's Soul Transferred from a Full Human Body to a Skeleton & still kept all of it's Human Functions)
And this is Hinted by the Fact they are named Seraphims & also their Designs which are reference to Angels who carry God's Throne in Christianity & Judaism (Similar Concept also exists in Islam), which is what their entire Existence revolves about, just serving God & carrying his Throne. So i believe that Lunarians also had their National Treasure which is something Godly, something they Worshipped & it's most probably their Power Source (The Place/Body that they can connect to through their Flames)
Imu (Which in Katakana can mean Buddha) was the one who took their Treasure as his/her Power
Which is most probably a "Divine Light/Sun/Flame", you can say that Imu is Queen of Divine Light
And that's Hinted so many times:
Enies Lobby has a Permanant Day (Maybe it's Sun is Man-Made & have been created by Imu)
Imu was seen in Room of Flowers which just like Ryokugyu hints at Light-Related Powers (Photosynthesis)
Oda made Kizaru who has Light Ability the Most Loyal Servant of CDs among Admirals (He is a Light who serves Greater Light)
Gorosei specifically used the Word "Light" when they talked to Imu
Giant Straw Hat was seen under a Ray of Light (Contrary to Rest of entire Room & other similar Spaces)
What Destroyed Lulusia Kingdom did indeed look like a Laser, so the Idea of Imu having Divine Light isn't far-fetched at all
Pacifista & Seraphim who serve Gorosei all have Kizaru's Powers (A Fraction of it ofc), just like Kaidou had an Army of Beasts (Same Theme)
Lunarians is Reference to Moon which Reflects the Sun's Light, so it makes sense that Lunarians's Powers are actually Reflection of their God
And there are many other Hints
So Overall, Lunarians are connected through a Holy Fire/Place/Body/Light/Sun, that is their God & it's Invincible
Lunarian's Worship is basically giving away their Power Source to this God, in exchange for Temporary Invincibility
So Flames On & Off are like Lunarians Prayers
It's also why their Skins are Dark, cuz that's how it became due to that Divine Light/Sun they Worship, it made all their Skins Darker.
Based on all this, it's possible that Disrupting their Connection with the Holy Source is what can counter their Invincibility
Since it's a Spiritual Connection rather than a Physical One, then a Soul going inside their Bodies such as Zeus or Brook might Disrupt that Connection & cause them to lose some of their Invincibility (Similar to how Two DFs can't co-exist in same Body)