Simplify the following text for a Grade 11 native English-speaking person.
Original: Initially the friendship formed in the mid-1860s between Pissarro and CÃ zanne was that of master and disciple , with Pissarro exerting a formative influence on the younger artist .
Simplified: Initially the friendship was that of master and disciple , with Pissarro exerting an influence on the younger artist .