svayam ātmā — Kṛṣṇa, who is personally the Supreme Soul, the Supersoul; ātma-go-vatsān — now expanded into calves that were also He Himself; prativārya ātma-vatsapaiḥ — again He Himself was represented as the cowherd boys controlling and commanding the calves; krīḍan — thus Himself constituting everything in these transcendental pastimes; ātma-vihāraiḥ ca — enjoying Himself by Himself in different ways; sarva-ātmā — the Supersoul, Kṛṣṇa; prāviśat — entered; vrajam — Vrajabhūmi, the land of Mahārāja Nanda and Yaśodā.

Translation

“Now expanding Himself so as to appear as all the calves and cowherd boys, all of them as they were, and at the same time appear as their leader, Kṛṣṇa entered Vrajabhūmi, the land of His father, Nanda Mahārāja, just as He usually did while enjoying their company.”

Bhaktivedanta Purport

By Śrīla Prabhupāda

Kṛṣṇa usually stayed in the forest and pasturing ground, taking care of the calves and cows with His associates the cowherd boys. Now that the original group had been taken away by Brahmā, Kṛṣṇa Himself assumed the forms of every member of the group, without anyone’s knowledge, even the knowledge of Baladeva, and continued the usual program. He was ordering His friends to do this and that, and He was controlling the calves and going into the forest to search for them when they went astray, allured by new grass, but these calves and boys were He Himself. This was Kṛṣṇa’s inconceivable potency. As explained by Śrīla Svarūpa Dāmodara Gosvāmī, rādhā kṛṣṇa-praṇaya-vikṛtir hlādinī śaktir asmāt. Rādhā and Kṛṣṇa are the same. Kṛṣṇa, by expanding His pleasure potency, becomes Rādhārāṇī. The same pleasure potency (ānanda-cinmaya-rasa) was expanded by Kṛṣṇa when He Himself became all the calves and boys and enjoyed transcendental bliss in Vrajabhūmi. This was done by the Yoga-māyā potency and was inconceivable to persons under the potency of Mahā-māyā.