Italian to English Social Sciences History

The following sentence from a 16th century text by Paolo Giovio, Commentario de le cose de' Turchi, is leaving me very confused. The context is a discussion between the Turkish sultan Bayazet and two counselors about the ongoing conflict between his two sons, Selim and Acomat. The sentence reads: "Questi dui persuaseron a Baiazeto che perdonasse a Selim che lo facesse venire e gli desse l'impresa contra Acomat, dicendo che la cosa ad ogni modo reuscirebbe bene ancor che Selim rimanesse perditore perché in tal caso un tristo si castigarebbe con l'altro."

My attempt at a translation so far is: "These two convinced Bayazet that he should have forgiven Selim, that he should have summoned him and given him the enterprise against Acomat, saying that it may be successful even if Selim were defeated, since in that case one knavish [or simply, nasty] deed would punish itself with another."

I have posted this question already on the forum at WordReference.com, but I am not completely satisfied with the answers. For what it's worth, here they are:

"These two convinced Bayazet to forgive Selim, and got him to come, giving to him(Selim) instead of to Acomat the enterprise, saying that everything would turn out well even if Salim stayed lost, because in that case one bad deed would be the punishment for another."

"These two exhorted Bayazet to forgive Selim, summon him at court and "give him the enterprise???" against Acomat, saying that it would be a success even if Selim were defeated, since in that case the two "tristi??" would punish each other."

Thanks for any help.