Complex sentence: Estes continued Knudsen's work of making Pontiac a performance-car brand until 1964, when John DeLorean replaced Estes as general manager, and he too continued in the same direction.
Split into simpler sentences: Estes continued Knudsen's work of making Pontiac a performance-car brand. In 1964 John DeLorean replaced Estes as general manager and continued in the same direction.