Complex sentence: Accountants can choose it to implement a financial capital concept of invested "purchasing power" instead of invested money where under they measure financial capital maintenance "in units of constant purchasing power" instead of the traditional Historical Cost nominal monetary units.
Split into simpler sentences: Accountants can choose it to implement a financial capital concept of invested "purchasing power" instead of the traditional Historical Cost concept of invested money. They will thus implement a constant purchasing power financial capital maintenance concept by measuring financial capital maintenance "in units of constant purchasing power" instead of the traditional Historical Cost nominal monetary units.