Translate Geometry generator expression into Virtual layer Query

Question

I have some expressions for drawing tree canopy zones ultimately I want to merge the zones for trees, hedges and woodland together but for now I would be happy if I can get the following expression to work as an SQL query to generate a virtual layer. I am new to virtual layers but have managed to create a basic buffer, however when I try to build up my canopy expression the query runs but either generates nothing or points only.

This is my main expression

union(
    difference(
        buffer(
        case
            when  "EvenCan" is null
            then
                translate(
                            buffer( 
                                smooth(
                                    make_polygon(
                                        make_line(
                                        Project($geometry, "n" ,Radians(0)),
                                        Project($geometry, "e",Radians(90)),
                                        Project($geometry, "s" ,Radians(180)),
                                        Project($geometry, "w" ,Radians(270))
                                        )
                                    )
                                ,5)
                            ,(("n"+"e"+"s"+"w")*0.058),8)

                
                ,0 , 0 )
            when  "EvenCan" is not null
            then buffer($geometry,"EvenCan")

        END
        ,2)
    ,aggregate('Zone_2_subtractions_4e7a378a_1173_41b7_bfdd_e98a0218a2c7','collect',$geometry)
    )
,aggregate('zone_2_additions_3e32c88c_f49b_4b5f_9bf5_8253da06c30e','collect',$geometry) 
)

I have tried to translate the basic bit as follows but that generates an empty layer

select

make_polygon(
    make_line(
    ST_Project(geometry, n,Radians(0)),
    ST_Project(geometry, e, Radians(90)),
    ST_Project(geometry, s,Radians(180)),
    ST_Project(geometry, w,Radians(270))
    )
)
from
BS_TreeSurveyData_df898e14_a741_43f7_aaa8_8f268457f6d8