Incompatibilities between Vatican II and the Council of Florence on salvation outside the Church?

*I am aware of [this](https://christianity.stackexchange.com/questions/28431/do-the-catholic-church-ex-cathedra-pronouncements-about-necessity-of-catholicism/28433#28433) previous question where the discussion centered on statements of Pope Francis and the catechism but that is not my interest here. [This](https://christianity.stackexchange.com/questions/30898/has-the-church-stated-any-advantages-or-reasoning-or-prompting-to-re-formulating/30899#30899) question also asks about the reasoning behind these changes but that is also not my question.* From what I understand about Catholic teaching, it is not possible for infallible teachings, either from a pope or an ecumenical council, to contradict each other. However, there seems to be a clear incompatibility between medieval Catholic doctrine and that of Vatican II around the question of salvation outside the church: [Pope Boniface VII, Unam Sanctam (1302)](https://www.papalencyclicals.net/bon08/b8unam.htm) > Furthermore, we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff. [Council of Florence, Session 11 (1442)](https://www.papalencyclicals.net/councils/ecum17.htm) > It firmly believes, professes and preaches that all those who are outside the catholic church, not only pagans but also Jews or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the catholic church before the end of their lives. Contrast this with two documents from Vatican II in 1964: [Vatican II, Decree on Ecumenism](https://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decree_19641121_unitatis-redintegratio_en.html) > It follows that the separated Churches and Communities as such, though we believe them to be deficient in some respects, have been by no means deprived of significance and importance in the mystery of salvation. For the Spirit of Christ has not refrained from using them as means of salvation which derive their efficacy from the very fullness of grace and truth entrusted to the Church. [Vatican II, Pope Paul VI, Lumen Gentium](https://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19641121_lumen-gentium_en.html) > But the plan of salvation also includes those who acknowledge the Creator. In the first place amongst these there are the Muslims, who, professing to hold the faith of Abraham, along with us adore the one and merciful God, who on the last day will judge mankind. To me it seems fairly clear that the "schismatics" from the council of Florence would correspond to the "separated churches and communities" from Vatican II. Unam Sanctam makes even clearer that the intent of the earlier documents is that "salvation outside the church" does mean communion with the Roman Pontiff, despite Vatican II's discussion of separated communities and Muslims. Admittedly I do not understand the intricacies of Catholic thought on many matters so my question is: How can all of these documents be read together consistently within a Catholic framework? In particular I'm interested in how this can be consistent with the infallibility of ecumenical councils and papal infallibility.