Complex sentence: Both CPPA and CIPPA are price-level accounting models which use the principle of financial capital maintenance units of constant purchasing power to maintain the real value of all non-monetary items during hyperinflation and only constant real value non-monetary items during low inflation and deflation respectively.
Split into simpler sentences: Both CPPA and CIPPA are price-level accounting models which use the principle of financial capital maintenance in units of constant purchasing power. Under CIPPA only constant real value non-monetary items (not variable real value non-monetary items) are measured in units of constant purchasing power during low inflation and deflation respectively.