In fact the puzzle is as simple as it is literally and needs no additional explanation.
You got plaintext, you got ciphertext, you got substitution table, and then you backpropagate from another ciphertext to another plaintext, and now you have two plaintexts, and you're the winner.
But not everyone here can figure out multisig wallets and BIP39, I guess.
So what's the harm in writing more?
The real puzzle is to understand the puzzle. Not a good puzzle if it needs so much explaination imho.
Good look everyone. I skip.