Crappy unreliable translation until a better one comes along.
Despite being crew mates they fight all the time. All they ever do is badmouth each other.
But they believe in only one possible future (that Luffy will be pirate king).
When faced with an overwhelming opponent Sanji entrusts him (kill him if he turns evil).
Zoro swears to uphold that promise.
I think that's what it says. I apologize if I'm fake news.