Achievements are goals or landmarks that have been reached , typically through effort eg., passing your degree , wining a gold medal etc.
Accomplishments are both simple and tough tasks that have been completed by a person
You dont read a lot , and yet you finished this book . That is quite an accomplishment on your part ( something you have done successfully )
You dont read a lot , and yet when you said you would finish this thick book , you really did it .Thats quite an acheivement on your part ( your successfully do something you set out to do by great effort)