Chelsea is the least club in performance among this other clubs, I'm still surprised how Chelsea managed to be able to remain in Champions league even with their bad performance.
Chelsea won over Dortmund even they got bad result in the first leg. It has two reason, they played better in a second leg at Stamford Bridge and Dortmund did not play well enough to secure their advantage from the first leg.
However going through quarter finals, every club have their chance to go to semi finals and even take the trophy in this season. Chelsea will have to recall about what they got in the past season in two matches with Real Madrid. Especially the second matches in Bernabeu when they even led 3- 0 before letting Real Madrid to come back.
Napoli shouldn't have big problems about moving Milan out of their way in this round. There is a big difference between them already. Osimhen and Kvaratskhelia should be able to make difference as always. After that I would expect Napoli to have a matchup against Inter. And they can get past Inter as well and make it to the final round later on.
Napoli will have to be so careful with AC Milan even they are stronger and have better form, carefulness has its value and importance for Napoli in knock-out matches. AC Milan with their history knows that in Champions League, a stronger club are not always winner. I believe AC Milan will have appropriate tactics like Catenaccio to reduce space for Napoli and dangerous attacks from Napoli. After that they can wait for chances from counter attacks that can make them as winner.