you can use fixed contour operation with these alternative drive methods
radial cut - use one of the two curves as the drive.The cut pattern ,of course, will be radial to the curve, you can choose the stepover and the witdth of the worked area
surface area - you have to build a surface ( a ruled for example) between the two curves. ( tip: depending on the version you are using, it is better, before constructing the surface, to set Preferences -> Modeling -> Freeform -> Freeform Construction Result -> B-surface ). After you have constructed the surface you can use it as the drive geometry and choose cut direction, cut pattern, stepover and so on.
streamline - select the two curves as Flow1 and Flow2 and choose pattern, cut direction stepover etc. In this particular case this drive method is similar to surface area, with the advantage you don't have to build the ruled surface.
boundary - select the curves as closed boundary (Depending on the version you are using you must close the gaps between the two curves with lines) Be sure to select the curves with Tool Position = On, then choose Radial zig-zag as pattern, the center point for the pattern, the stepover and so on