Simplify the following text for a Grade 7 native English-speaking person.
Original: Major success came in 1963 with the Lotus 25 , which â '' with Jim Clark driving â '' won Lotus its first F1 World Constructors Championship .
Simplified: They had big success in 1963 with the Lotus 25 . With Jim Clark driving , Lotus its first F1 World Constructors Championship .