Marco did NOTHING that prove he is Stronger than king or Queen.
He Just hold them for a MOMENT to send zoro to the rooftop. THE END.
The amount of examples in One piece where hold, block, push means NOTHING in terms of strenght is INFINITE.
So If you think that somehow proves that Marconis stronger than king or Queen you DUMB.
Marcos can eventually be stronger? Sure, but not until now. NOTHING proves that.