Ezekiel 21:26

The term "diadem" is used of the mitre of the high-priest, Exodus 28:4. There can be no reference to the high-priest here, the passage refers exclusively to the royal house, which shall be discrowned.

this … the same The somewhat enigmatical words mean probably: this is not that, i.e. the present royal house and régime is not that which shall be (the Messianic), as Ezekiel 21:27 explains. Or, this shall not remain this, i.e. what it is, it shall be removed and give place to something higher to come, Ezekiel 21:27.

exalt… that is high let that be exalted which is low, and that which is high be abased. The words "overturn," &c., Ezekiel 21:27 explain the idea. The present order shall disappear, the high shall be abased and at last that which is humble shall be exalted, cf. Ezekiel 17:24.