The one thing I feel slightly lessens this puzzle is that the knight promotions are defensive moves, the task of moving the bishop around to find a new checkmating square is easy. I prefer UnderPromotion puzzles where the side with the objective is the one having to make multiple UnderPromotions, like this one:
Any other promotion at any point doesn't just not win, it loses! Hard to beat this one!
great puzzle and hats off for "Tal" the magician of riga