Large helicoid(28~75mm) = M42->Z (turned 15 degree)
Small helicoid(11~18mm) = M42->M42 (fully contracted)
Both together at infinity position in this photo
Of course M42->Z adapter alone works fine actually,
also slightly smaller and a bit lighter for carrying.

(shot by D800E + AF Micro Nikkor 200mmF/4D @f11)