No, he doesn't.
That's just your headcanon.
Yes, he thinks that way, Nik.
But it refers to the difficulty of fulfilling the dream, not to the power. To be the king of the pirates we already know what to do, and you need power, allies, information, contacts, luck, and much more.
Difficulty: KoP > WSS
Power: WSS >KoP
To put a situation easier to understand. Luffy defeated Kaido, an obstacle to being the king of the pirates, but how did he do it? With an alliance, with Kaido facing more enemies, etc.
Zoro cannot or should not have help against Mihawk, nor can he make alliances, nor make plans, nor expect anyone to weaken or drain Mihawk's energy, he simply must do it alone. Without his friends, without allies, without information or anything at all.
hell, even just without Robin he can't fulfill his dream xd