1 - Did Queen coat his? Both didn't, or both did with invisible haki. The the comparison stands, unless you decide to cherry pick in order to downplay Sanji. That'd be really dishonest.
2 - That's merely a conjecture. Prove that Zoro's endurance improved from that training.
3 - Anything can be said to be overrated if you choose to pay attention to delusional fans. I've seen Zoro fans state that he's tronger than Kaidou and that he's the strongest in the verse, that pre TS Zoro is stronger than current Sanji... See? Everything about Zoro is overrated following your logic.
4 - Prove that it being a pointy weapon matters. Zoro was hit in the torso, an area with a natural armor. Where's the natural armor in the skin?
5 - Yes, that was a massive feat. Sanji's endurance feat was superior to Zoro's in a similar situation and you're doing your best to downplay Sanji.
6 - Zoro COULD be able to do something Sanji did EFFORTLESSLY by using haki. While Sanji didn't despite being able to. Somehow you think this is a great argument to downplay Sanji, when in reality it means he probably surpasses Zoro in ONE SINGLE STAT.
Yes, it was a great feat. People like you just have a pathological necessity to downplay anything Sanji does.