Original: His biggest commercial success came with the action adventure horror film (co-starring Rachel Weisz) The Mummy (1999) and its sequel The Mummy Returns (2001), both of which were hugely successful at the box office.
Simplified: His best success was with the film (which also had Rachel Weisz as an actor) called The Mummy in (1999) and its sequel The Mummy Returns (2001), both of which were very successful.