Prepare simple syrup: Combine sugar and water in a small saucepan. Bring to a simmer over medium, stirring occasionally, until sugar dissolves, 2 to 3 minutes. Remove from heat, and let cool to room temperature, about 30 minutes.

Blend the ingredients and freeze: Transfer simple syrup to a blender. Add frozen peaches and lemon zest and juice.

Blend until smooth and creamy, about 1 minute. Transfer to a shallow container or an 8- x 4-inch loaf pan.

Cover and freeze until firm, about 4 hours.

Let stand at room temperature for about 10 minutes before serving. Sorbet may be stored in an airtight container in the freezer for up to 3 weeks.