Final answer:
The significant change starting with 'Flore et Zephyre' was the adoption of female dancers dancing en pointe, marking a major technical and artistic development in ballet history.
Step-by-step explanation:
A major change to ballet starting with "Flore et Zephyre" was D) The adoption of female dancers en pointe. Before this period, ballet was characterized by styles that included ornate posturing and stylized dance forms.
The shift to dancers performing en pointe represented a significant technical and stylistic development in the history of ballet and was a part of broader changes that provided new opportunities for female artists to gain recognition in the arts.
This change enhanced the visual aesthetics of ballet, aligning with other trends that affected visual arts and performance, like the emergence of Les Trios Grandes Dames and the influence of Japonism on European artists.