What is a syntergist muscle o fthe zygomaticus?

A synergist muscle of the zygomaticus is the risorius muscle. While the zygomaticus major and minor are primarily responsible for elevating the corners of the mouth during smiling, the risorius assists by pulling the mouth laterally, enhancing the expression of joy or amusement. Together, these muscles contribute to facial expressions, particularly in the lower part of the face.