Oxygen isotope effect in disordered underdoped and overdoped La2−xSrxCu1−yZnyO4 superconductors

► Oxygen isotope exchanged Zn substituted La214 were used with different hole contents. ► Isotope exponents (IE) were extracted from the magnetization data. ► Hole content and disorder dependent isotope exponents were analyzed. ► The existing theoretical models can not explain the values of IE in the Zn doped overdoped compounds.