To what extent are they (in)compatible with each other? To what extent do their accounts reinforce, undermine, coincide with or complement each other? To what extent are their accounts (or might their accounts be) combinable into a superior (or at least a more comprehensive) account of these historical dimensions of human thought and understanding? To what extent do their respective insights and oversights help us better to understand or to resolve issues about the historical dimensions of human thought and understanding?
Hegel and Heidegger were both eminent philosophers of their respective times: Hegel (1770-1831), the earlier of the two, belongs to the school of Idealism whereas Heidegger (1889-1976) was one of the main exponents of 20th century Existentialism.
Hegel sees the development of Being as an infinite development cycle triggered by the intention of becoming something what it is not at present, and this perpetual chain of development is marked by a point of coincidence of being and non-being, which, when united, form a higher entity. The former entity is therefore combined, through the factors of being and non-being, in a higher synthesis of the two. The development of Being therefore consists of three stages: being is the thesis, non-being the antithesis, and the becoming is the synthesis. These stages are repeated ad infinitum so that the new Being is again tested by the non-being and achieves a still higher stage in the melding of thesis and antithesis to a new stage of becoming. Being is therefore in a constant state of flux, it is rebuilding itself ad infinitum to achieve higher stages of itself. The former stages of Being are not nullified but re=evaluated, so in the development of the human personality we pass from one state to another, constantly evaluating and developing our personality, passing from state to state without nullifying the previous state, which is constantly dividing and recomposing itself.