I am GOD, and not man. Figure of speech Pleonasm (App-6): put both ways for emphasis. Reference to Pentateuch (Numbers 23:19). Compare Isaiah 55:8; Isaiah 55:9; Malachi 3:6.
GOD. Hebrew. 'El. App-4.
man. Hebrew. 'ish. App-14.
in the midst. [will not come] into the midst. Reference to Pentateuch (Exodus 33:5). App-92.
enter into. come against: i.e. as an enemy. The verse is not "nonsense", as alleged. The reference is to Hosea 11:8.
the city: i.e. as. came against Sodom and Gomorrah.