I don't really care about the D clan in relation to Zoro or the Shimotsuki tbh, BUT they obviously could be D members. Everything we know about the D clan so far fits the Shimotsuki.
Look at Ryuma. We know that Ryuma SINGLEHANDEDLY kept the ENTIRE WG out of Wano while he was alive. The D clan is the enemy of the gods (celestials). So a man that is a one man army opposing the world government obviously fits into the D clan.
Anyways, D clan aside, I am 100% certain Zoro is a Shimotsuki and that it will hold some relevance within Wano.
At the very least I expect Gyukimaru and the Yakuza bosses to bow to Zoro or smth similar as Yasuie, a Shimotsuki, was the respected boss of all of them and a generally supremely respected figure in Wano.
Is Zoro the second Ryuma? 100% as well.
Ryuma literally looks like Zoro with black hair. They look 100% the same. Literal twins. They're even both confirmed to be one eyed swordsmen with the newest chapter.
Also Oda was saying in a magazine before that after Zoro received Shusui from Ryuma, a new legend of slaying an EASTERN DRAGON may be forged.
And ofc there is also the infamous line of "May a person that people call the second Ryuma have already been born?" in one of the magazines.
Historically speaking Zoro holds comparable weight in this country to Momo right now tbh. Generally I would say the Shimotsuki are more important because of Ryuma specifically, Ryuma is the man that made Wano survive at all. But obviously with the more recent historical context the Kozuki are at the center of the conflict.
And another thing that will definitely be very important imo.
Hyogoro is the one that points out Zoros similarities to Ushimaru and Ryuma. The same Hyogoro that is the respected Yakuza boss that has command over pretty much all the samurai in Wano right now. If anyone can make the people INSTANTLY believe in Zoros importance, it is Hyogoro.
So I believe Hyogoro will somehow tell the samurai that Zoro is the heir of the Shimotsuki and all the samurai will instantly accept Zoro as their authority/lord for the battle.
Zoro doesn't seem to try and seize command, like he said back on Zou, so I think someone else, Hyogoro, will give him that command.
Quality content as always bro. I honestly only use WG when I got an alert that you tagged me xD