Zygarde-10 with Aura Break is allowed to have Iron Tail, Superpower, Spite, and every other Generation 6 tutor move on PS's postbank metas. This is not possible due to the nature of the Zygarde assembly in Sun & Moon.
Zygarde-50 can only change into Zygarde-10 if it has Power Construct. Once a Zygarde has Power Construct, it can never be changed to Aura Break. Getting Power Construct onto Zygarde requires either only the cells in the Zygarde Cube or a Zygarde on top of those cells. Selecting Zygarde + cells enables it to keep its moveset. Once you assemble Power Construct Zygarde, you can change it to 10% forme with the Zygarde Cube. This is the only way to get Zygarde-10 with past gen moves.
Zygarde-10 with Aura Break, however, cannot be obtained by transferring a past Gen Zygarde-50 and changing its forme. While going from 10 to 50 with Aura Break is possible, the reverse cannot happen. The game doesn't let you subtract cells from a zygarde, but you can disassemble it and attempt to create a new Zygarde. However, by separating a Zygarde, it loses everything and when you reassemble it, you get an entirely new Zygarde. Zygarde-10 with Aura Break is Alola-exclusive and cannot have past gen tutor moves.
Zygarde-50 can only change into Zygarde-10 if it has Power Construct. Once a Zygarde has Power Construct, it can never be changed to Aura Break. Getting Power Construct onto Zygarde requires either only the cells in the Zygarde Cube or a Zygarde on top of those cells. Selecting Zygarde + cells enables it to keep its moveset. Once you assemble Power Construct Zygarde, you can change it to 10% forme with the Zygarde Cube. This is the only way to get Zygarde-10 with past gen moves.
Zygarde-10 with Aura Break, however, cannot be obtained by transferring a past Gen Zygarde-50 and changing its forme. While going from 10 to 50 with Aura Break is possible, the reverse cannot happen. The game doesn't let you subtract cells from a zygarde, but you can disassemble it and attempt to create a new Zygarde. However, by separating a Zygarde, it loses everything and when you reassemble it, you get an entirely new Zygarde. Zygarde-10 with Aura Break is Alola-exclusive and cannot have past gen tutor moves.