To be very honest, Chopper going head to head with Zoan Queen for 1 hour+ has removed any lingering doubts I had about Sanji not being strong enough to solo King.
Chopper went from getting neg diffed by Perospero to stalemating someone that's nearly double Peros' bounty.
Sanji beating both King and Queen might honestly be a smaller jump (it'll still never happen) than what is being implied for Chopper.
At any rate, Sanji is one of the "monster trio", while Chopper is a member of the "weak trio". Sanji is far more relevant as a combatant, so there's no more reason to doubt that Sanji can solo a Calamity.
And honestly, if Oda wanted King/Queen to be teamed up on, Drake could have pitched in. If he hasn't joined now, there's not much reason to expect him to do so later.
@Geo,
@Kuro Ashi,
@Topi Jerami,
@playa4321.