Also study Ateres Rosh.
In Likkutei Diburim the Study of Tikunei Zohar is mentioned
This shiur discusses that during the month of Elul, it is customary to study Derech Chayim by the Mitteler Rebbe. Additionally, it is recommended to study Ateres Rosh. Likkutei Diburim also mentions the practice of studying Tikunei Zohar during Elul.
Summary
In Elul, Chassidic custom emphasizes learning specific texts such as Derech Chayim and Ateres Rosh, and includes the study of Tikunei Zohar as mentioned in Likkutei Diburim.