Here is the full list of all 26 Zenodyne R achievements.
Defeat the Commander (Ending C!)
Beat the game using the fifth ship
Unlock unlimited credits!
Beat the game using the fourth ship
Unlock all the lore!
Beat the game using the third ship
Clear Final Stage Hard (Ending B!)
Beat the game using the second ship
Clear Stage 5 Hard
Clear Stage 4 Hard
Clear Stage 3 Hard
Clear Stage 2 Hard
Unlock the Fifth Ship
Unlock all the ships!
Clear Stage 1 Hard
Beat the game using the first ship
Unlock the Fourth Ship
Clear the Final Stage (Ending A)
Beat the game using the cameo ship!
Unlock the Third Ship
Clear Stage 5
Clear Stage 4
Clear Stage 3
Unlock the Second Ship
Clear Stage 2
Clear Stage 1