Students who want to major in physics must have sufficient knowledge of mathematics.

Literal

Physics [object-を] want-to-major students [topic-は], mathematics [possessive-の] knowledge [subject-が] sufficient must.

物理学を専攻したい学生 is a relative clause modifying 学生: 'students who want to major in physics.' 十分でなければならない applies ~なければならない to a な-adjective (十分な = sufficient).