Parallel machining leaves large scallops in regions where the toolpaths are tangent to the surface. To remachine the regions with large scallops:
Create two operations that machine in orthogonal directions (such as X parallel and Y parallel).
Set the Minimum Surface Slope in Direction of Toolpath to a large angle (like 45 degrees).
The second operation will now be limited to the steep regions of the part. These are the regions that contain large scallops from the previous operations.