所以園遊會不但是讓學生鍛鍊行銷能力的最佳時機，也是增進其他方面能力的好

所以園遊會不但是讓學生鍛鍊行銷能力的最佳時機，也是增進其他方面能力的好機會。

結果 (英文) 1:

Therefore, the garden party is not only the best time for students to exercise their marketing skills, but also a good opportunity to improve their abilities in other areas.

結果 (英文) 2:

Therefore, the park tour is not only the best time for students to exercise their marketing ability, but also a good opportunity to enhance other aspects of their ability.

結果 (英文) 3:

Therefore, the park tour club is not only the best time for students to develop their marketing ability, but also a good opportunity to improve their abilities in other aspects.