Does such a manouver exist, for any given Boom&Zoom plane? (I'm thinking mostly in the region of propeller aircraft WW2 era - the question may be relevant because these aircraft were designed with the propeller functionality as a definite design aspect)

I would think that the propeller controls (propeller settings) does become a factor at certain dive speeds, probebly dependant on the actual example plane though?

Definition of optimal in this case would be simply most energy retained possible (disregarding angular advantage for purpose of air combat advantage)

Presumably you would compare total energy state just before the dive attack, to the energy state at the end of the zoom-climb?

Presumably low G manouvers would be better for energy retention? (low G manover may not give you angles easily against opponent though, if it were only so easy I know!!!) Isn't this what the so-called "energy egg picture" tries to depict? (tactical egg, energy egg, showing flight paths of a plane, across horizontal and vertical)

Energy loss happens as you go faster (faster than you should?), drag increases? How much drag can be diminished, by properly manipulating the propeller? How much drag is inevitable, as a result of airframe drag?