I interpret Wings of the Pirate King to mean the strength each wing has under him which will enable Luffy to fly.
For Sanji he has Germa 66. Obviously by the time Luffy becomes Pirate King, Zoro will most likely be World Strongest Swordsman level by then. Therefore, the wings don't necessarily mean Zoro and Sanji are equal in strength individually.
Robin in my opinion is the smartest in the crew, and could even confidently call Sanji's influence equal to Zoro without even being part of Whole Cake. The fact Robin said it in Chapter 1020 in the middle of the raid means she already understands Zoro's future influence related to Wano.
Does this mean Zoro will lead the Scabbards during the war in the future? Does this mean Sanji's family is equal to the Scabbards in power? Does the Nika silhouette with a sword in his right hand and a spear in his left represent Zoro and Sanji, after all Luffy's spear move does only use his legs?