不亦乐乎 (bú yì lè hū): Isn't it joyful? / Isn't it delightful? (phrase) — Meaning & Stroke Order

The children are running around in the park with great joy.

He was not busy with trivial matters to the point of delight; instead, he focused on the core tasks.

The volunteers organized community activities, with everyone dividing the work and cooperating, busily and joyfully.

He is busy preparing for the party and enjoying it immensely.