The recommended order replacement of the RailCore II ZL series 3D printed parts with aluminium replacements is:-

1. X Carriages, Idler pulley mount set & Stepper mounts - recommended for ZL and highly recommended for ZLT
2. (ZL only) Hotend mount
3. Z Yokes - highly recommended for ZLT
4. Z Brackets - reported as useful for hitting higher speeds
5. (ZLT only) Hotend mount
6. Magnetic heated bed
7. Halo - doesn’t seem to improve prints, but does pre-align belts
8. Aluminum Y carriage - lighter than the printed part, and saves you weight

Longest swap times after assembly

1. Magnetic heated bed - if possible, try to incorporate this into your inital build.
2. Z brackets
3. Halo