Contradiction with Jeremiah 1:7
This verse describes God directly commanding the prophet, which can be seen as differing from symbolic acts in Zechariah 6:9.
Jeremiah 1:7: But the LORD said unto me, Say not, I [am] a child: for thou shalt go to all that I shall send thee, and whatsoever I command thee thou shalt speak.
Contradiction with Ezekiel 4:9
God instructs Ezekiel to perform a symbolic act, while in Zechariah 6:9, the instruction is to perform a symbolic act which might be seen as mere articulation.
Ezekiel 4:9: Take thou also unto thee wheat, and barley, and beans, and lentiles, and millet, and fitches, and put them in one vessel, and make thee bread thereof, [according] to the number of the days that thou shalt lie upon thy side, three hundred and ninety days shalt thou eat thereof. [fitches: or, spelt]
Contradiction with Exodus 4:10
Moses hesitates to speak for God due to perceived inadequacy, contrasting with Zechariah's direct receipt of word from the Lord in Zechariah 6:9.
Exodus 4:10: And Moses said unto the LORD, O my Lord, I [am] not eloquent, neither heretofore, nor since thou hast spoken unto thy servant: but I [am] slow of speech, and of a slow tongue. [eloquent: Heb. a man of words] [heretofore: Heb. since yesterday, nor since the third day]