O boy...
They are seriously dead now, but 'the enemy of my enemy is my friend' concept maybe at work here...
Lowkey, I hope Sanji and the Strawhats bail out with Reiju and leave the Vinsmokes to deal with this on their own.
Now I think If Sanji had kicked Capone's a** back at Zou they would have some fighting chance aginst BM's crew(wit dukes,Zunisha,Luffy etc fighting against BM's crew) whereas now they are basically doomed who are waiting for their execution
Not so really. If Sanji had kicked Capone's ass, then Big Mom would have started hunting them for revenge. That would still leave them being hunted by two Emperors and it's not like they can stay on Zou forever. Zou as a whole barely managed to survive a single fleet from Kaido's crew, and it's not like Sanji was aware of the Strawhat Fleet or Zunisha's ability to fight back.
Considering that Zou's warriors barely managed to survive Jack's invasion, I don't know if it's feasible to say that they'd be able to put up a good fighting chance against several Emperor fleets or the entire crew of one, assuming Big Mom gets pissed off enough for that. The Strawhat Grand Fleet could probably help, but again Sanji doesn't know about them and I can't really remember how strong they are.
It'd also depend on if the Vinsmokes would be aware of Big Mom's secret plan, which I don't see happening. They'd probably keep lying to them and have the Vinsmokes join them in hunting Sanji to force him to Whole Cake to complete the massacre, or they might try to find another way. Can't say for sure.