I will try something and bet on the opposite of bookmakers favor in two of these matchups. One will be West Ham and the other one will be Roma.
Milan - Roma should already be considered as a really close matchup though. Unlike the gap between their championship odds I see them having near equal chance. Roma are much better as you have also mentioned. Milan are a really challenging opponent for them here maybe but this time they have a bigger chance with De Rossi.
If De Rossi let Roma play attacking in quarter finals, it will be very risky for Roma because AC Milan are experienced enough in knock out matches and they have enough star players to punish any mistake from Roma players.Milan - Roma should already be considered as a really close matchup though. Unlike the gap between their championship odds I see them having near equal chance. Roma are much better as you have also mentioned. Milan are a really challenging opponent for them here maybe but this time they have a bigger chance with De Rossi.
I agree their matches will be very balancing and they are challenging opponent for each other so to beat their opponent, they will need to play very excellently or need their opponent to make mistake and give them a big gift to score winning goals or perhaps mistakes from referees and VAR referees.
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Leverkusen are of course quite the favourite against West Ham on paper. However seeing them having big difficulties against Qarabag for some reason tells me to give West Ham a chance with a small bet. I'm doing this just for fun so let's see what happens. 
Leverkusen are stronger than West Ham but their matches against Qarabag are signals that Leverkusen have weaknesses that can be exploited by West Ham. Compare Qarabag and West Ham, West Ham are stronger and if Leverkusen repeats what they did in two matches with Qarabag, they will be knocked out by West Ham in quarter finals.