For MLA you would include up to three authors in your in-text citation and your works cited list, for example:

One of the key studies on this subject (Hill, Smith and Jones 88) explains…

If your in-text citations and works cited list has more than four authors, you can then use et al. (meaning ‘and others’) in your in-text citation, for example:

Research by Hwang et al. (41) shows that…

or

Hwang, Jin Kyoung et al. "Spanish-speaking English Learners' English Language and Literacy Skills: The Predictive Role of Conceptually-scored Vocabulary." Applied Psycholinguistics, vol. 41, no. 1, 2020, pp. 1-24.