You can do that in the non-sequential mode indeed.

Set up a source to shine on an object.

Set up the scattering properties of this object. 

Add a detector to record the data and launch a raytrace.



Here is what it looks like in the sample file ''ABg scattering surface.zmx'' attached when you open a shaded model:





You can then change the angle of your source and run a raytrace again to analyse the pattern for different angles.



Here is an article describing the different scattering models in Zemax OpticStudio: https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01415

Finally, here is an article which shows how to add the surface properties to objects: https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01353