Well for one considering this is a made up technique that Zoro has no feats in being able to do it's not that hard.
How about dodge? He's not a slow golem like Pica.
Also you say there's no proof Smoker will keep chasing Luffy? How about the fact Smoker has never stopped chasing Luffy and it makes no sense story wise for him to stop as it's in character for him to do so. Not to mention Luffy has never defeated Smoker and the fact Luffy states he wouldn't want to fight Smoker unless Smoker was at full power implies itself Smoker is a challenge to Luffy.
You say Smoker may stop chasing Luffy after Punk Hazard? Because to me it makes sense that Smoker would keep chasing Luffy considering the two had been fighting since East Blue do you really think Oda would throw away the character development the two have had because
you think Smoker is now going to stop chasing Luffy? Nope ever since the timeskip Smoker has been portrayed next to Law and Luffy.
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Now say what you want since time skip Oda has made it clear that Smoker is the marine rival for the Worst Generation and is also going to get stronger (foreshadowed by Vergo) in order to protect his men all the while chasing Luffy like how Garp did with Roger.
Zoro struggled to pull off a 1080 cannon so he can't pull of the same technique with 3 times the power yet. Also Law's mountain slice was more impressive than the 1080 cannon which actually didn't even finish off Pica.
Vergo was over powering a heartless Smoker so what's your point? There's no evidence to suggest someone is weaker without their heart.
No I think your ignoring chapters and pages completely the fight between Smoker and Vergo was only shown really in 3 panels and 2 of them had Smoker getting the better of Vergo and it wasn't until Smoker went for Law's heart did he get defeated.
1)
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Smoker sending Vergo to the floor after beating him in speed, notice how Vergo is shown holding his head on the side blood was coming out it implies Smoker was the one who did that.
2)
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Smoker sending Vergo flying yet again with an elbow also causing Vergo to bleed.
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Do you see Vergo's statement? 'Those tactics aren't like you Smoker-kun' implying Smoker has another objective or if you like isn't fighting how he would usually fight which is another way of saying that Smoker is a lot stronger when he fights with his usual strategies.
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Do you see Smoker's arm going towards Law in the upper left panel the reason Smoker was hit in this page ultimately ending the battle was because he wanted to be hit he was fooling Vergo into believing he was going into an all out attack when in fact he was using the attack to get Law his heart back.
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See in this page Smoker stating 'Now we're even'? that implies Smoker had a reason to get Law's heart back and if you look on the same page you'll see the exact reason why since Law answers the question.
'You hate being in debt to a pirate that much... which shows Smoker from the start wasn't aiming to beat Vergo he was aiming for Law's heart so Law could get out his one hit finish attacks in which had Vergo not been so arrogant in believing his Haki could block it he would have been able to dodge.
Another thing is Vergo finally realizes what Smoker's plan was from the beginning and even comments on it in the upper right panel of the last page.
Now I don't know what manga you've been reading however these pages alone show Smoker putting up a good fight against Vergo despite Smoker's objective to not beat Vergo and retrieve Law's heart. In fact the anime made Smoker look far weaker.
I don't think you quite grasp the difficulty in fights not to mention...
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Luffy stating himself if Smoker can't go all out the fight would be annoying implying in his own body and at full power Smoker would be a challenge for Luffy and another little side note...Smoker while in Tashigi's body forced Luffy to go Gear 2nd and was also able to hit Luffy.
So now you think Smoker is weaker than Sanji now I know your mad.