ZOE is not used for permanent cementation because of?
DISADVANTAGES

It does not adhere well to enamel and dentin; hence, it causes microleakage and cannot be used for interim and long-term restorations.
Due to its low strength and high solubility, it cannot be used for permanent cementation(1st choice will be low strength then low solubility if asked in exams).
Its solubility is highest among all cements.

Ref: Materials used in dentistry, S. Mahalaxmi pg 267
Less strength
High solubility
Poor marginal seal
Poor pulpal protection