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