Okay, so you are playing cards in some weird environment where the hand you play in the poker game must be the same hand you play in the blackjack game. In other words, the same five cards in your hand (I know, sometimes blackjack hands are more or fewer than five cards) must be used for both the poker and blackjack hands.
So, what is the best possible 5 card hand for both poker and blackjack?
I have surmised that it is the four 5s and an ace: 21 in blackjack and a four of a kind, ace high for poker.
You cannot beat that hand. Can you?