It's the masculine personal plural form of 'duży'.

See the declension table at https://pl.wiktionary.org/wiki/duży (unfortunately the English wikitionary page contains a mistake)

NB all other adjectives which end on -ży in masculine singular form will have the same masculine personal plural form (e.g. 'świeży chłopiec' - 'świeży chłopcy'). 'Duży' is the only exception to this rule.

Because this adjective was borrowed from Ukrainian. Original Polish adjectives end on -ży and -że: świeży rekruci, świeże owoce, boży bojownicy, boże dzieła, chyży biegacze, chyże dziewczyny.

Because adjectives that modify plural 'personal masculine' nouns, such as "ludzie" take an -i ending. "duża osoba" > "duzi ludzie", but "duża kobieta" > "duże kobieta". See LearnPolish24.com - Adjectives - https://learnpolish24.com/home/artykul/1646/adjectives