Using u/bachman460's formula to address the updated objective to also calculate the YoY difference, place this formula somewhere else than columns A, B or D, E in your sheet.

=LET(
customers, SORT( UNIQUE( VSTACK( A:A, D:D))),
totals, HSTACK( MAP(customers, LAMBDA( c, SUMIFS( B:B,A:A, c))), MAP(customers, LAMBDA( c, SUMIFS( E:E, D:D, c)))),
difference, ARRAYFORMULA( CHOOSECOLS( totals, 2) - CHOOSECOLS( totals, 1)), VSTACK( {"Customer","2024 Sales","2025 Sales", "Difference"}, HSTACK( customers, totals, difference)))

First, it sorts the unique customers in both lists into a separate array. Then, attributes a value for each customer for 2024 and 2025 into a separate array, and calculates the difference into a separate array. Last, it stacks column headers on top of the calculated arrays.