Contradiction with Numbers 18:7
Numbers 18:7 states that only Aaron and his sons are to perform priestly duties, whereas Ezekiel 44:15 mentions the Levites, the sons of Zadok, as the ones ministering in the sanctuary.
Numbers 18:7: Therefore thou and thy sons with thee shall keep your priest's office for every thing of the altar, and within the vail; and ye shall serve: I have given your priest's office [unto you] as a service of gift: and the stranger that cometh nigh shall be put to death.
Contradiction with Deuteronomy 23:3
Deuteronomy 23:3 prohibits Ammonites and Moabites from entering the assembly of the Lord, but Ezekiel 44:15 speaks of any Levites ministering.
Deuteronomy 23:3: An Ammonite or Moabite shall not enter into the congregation of the LORD; even to their tenth generation shall they not enter into the congregation of the LORD for ever:
Contradiction with Hebrews 7:12
Hebrews 7:12 speaks of a change in the priesthood with Jesus, while Ezekiel 44:15 emphasizes the Zadokite line of Levites.
Hebrews 7:12: For the priesthood being changed, there is made of necessity a change also of the law.
Contradiction with Jeremiah 31:34
Jeremiah 31:34 talks about a time when no one will need to teach another to know the Lord, which contrasts with the need for priests to minister and instruct noted in Ezekiel 44:15.
Jeremiah 31:34: And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.