If you are going to write a quotation that contains another quotation, you do it differently depending on whether it is a short quote or a block quote:

Short quotations

Write double quotation marks around the entire quotation and single quotation marks around the quotation inside the quotation:

• Bliese et al. (2017) noted that "mobile devices enabled employees in many jobs to work 'anywhere, anytime' and stay electronically tethered to work outside formal working hours" (p. 391).

Block quotations

For block quotations, quotation marks are not used around the entire quotation and then you use regular double quotation marks around the quotation inside the block quotation.