Sukadeva Gosvami has already stated that such calculations (to understand the material universe) would be very difficult even if one had a duration of life like that of Brahma

Expressions researched:
"Śukadeva Gosvāmī has already stated that such calculations would be very difficult even if one had a duration of life like that of Brahmā"

Srimad-Bhagavatam

SB Canto 5

While passing over the mountainous region from Mexico to Caracas, we actually saw so many mountains that we doubt whether their height, length and breadth have been properly measured. Therefore, as indicated in Śrīmad-Bhāgavatam by Śukadeva Gosvāmī, we should not try to comprehend the greater mountainous areas of the universe merely by our calculations. Śukadeva Gosvāmī has already stated that such calculations would be very difficult even if one had a duration of life like that of Brahmā.

SB 5.16.10, Translation and Purport

In the same way, west and east of Ilāvṛta-varṣa are two great mountains named Mālyavān and Gandhamādana respectively. These two mountains, which are 2,000 yojanas [16,000 miles] high, extend as far as Nīla Mountain in the north and Niṣadha in the south. They indicate the borders of Ilāvṛta-varṣa and also the varṣas known as Ketumāla and Bhadrāśva.

There are so many mountains, even on this planet earth. We do not think that the measurements of all of them have actually been calculated. While passing over the mountainous region from Mexico to Caracas, we actually saw so many mountains that we doubt whether their height, length and breadth have been properly measured. Therefore, as indicated in Śrīmad-Bhāgavatam by Śukadeva Gosvāmī, we should not try to comprehend the greater mountainous areas of the universe merely by our calculations. Śukadeva Gosvāmī has already stated that such calculations would be very difficult even if one had a duration of life like that of Brahmā. We should simply be satisfied with the statements of authorities like Śukadeva Gosvāmī and appreciate how the entire cosmic manifestation has been made possible by the external energy of the Supreme Personality of Godhead. The measurements given herein, such as 10,000 yojanas or 100,000 yojanas, should be considered correct because they have been given by Śukadeva Gosvāmī. Our experimental knowledge can neither verify nor disprove the statements of Śrīmad-Bhāgavatam. We should simply hear these statements from the authorities. If we can appreciate the extensive energy of the Supreme Personality of Godhead, that will benefit us.