Mich. Comp. Laws § 700.3410
If 2 or more instruments are offered for probate before a final order is entered in a formal testacy proceeding, more than 1 instrument may be probated if neither expressly revokes the other and neither contains provisions that work a total revocation by implication. If more than 1 instrument is probated, the order shall indicate which provisions control in respect to the nomination of the personal representative, if any. The order may, but need not, indicate how any provisions of a particular instrument are affected by another instrument. After a final order in a testacy proceeding has been entered, a petition for probate of another instrument of the decedent shall not be entertained, except incident to a petition to vacate or modify a previous probate order and subject to the time limits of section 3412.
MCL 700.3410