Complex sentence: By 2004, Cavalier-Smith had created a new phylum, Miozoa, within the infrakingdom Alveolata, demoted Dinozoa and Apicomplexa to subphyla, and assigned them to the newly created Miozoa.
Split into simpler sentences: By 2004, Cavalier-Smith had promoted Alveolata to the status of infrakingdom and created a new phylum, Miozoa, within the newly promoted Alveolata. He also demoted Dinozoa and Apicomplexa to subphyla, and assigned them to the newly created Miozoa.