It should not be perceived that the Lubavitch Yeshivah has a lower learning standard

Studying Eitz Chaim on your own can lead to mistakes; study Chassidus instead. I cannot give an opinion on The Sulam on the Zohar, but we have the path of our Rebbes. Pnimiyus HaTorah (the inner dimension of Torah) can sometimes be included in the various categories of Torah study. https://www.torahrecordings.com/rebbe/igroskodesh/011/010/3663