Requirements for travel between Mexico and the US are covered by the "Western Hemisphere Travel Initiative". That website states in part that :
U.S. citizens and citizens of Canada, and Bermuda traveling by air
between the U.S. and Canada, Mexico, Central and South America, the
Caribbean, and Bermuda are required to present a valid passport or
other WHTI-compliant documentation to enter (or depart) the U.S
One of the "other WHTI-compliant documentation" items listed is a US Permanent Resident Card (Form I-551) - or a Green Card - which you have stated you do have. So as far as leaving and returning to the US by air, you are covered without a passport.
In general Mexico also accept a US Green Card for entry, although I'm not certain that this also applies for Mexico citizens. However even if it does not, then your Mexican Voter's Card IS acceptable for entry, presuming it has a photo on it.
The only thing I'm not sure about is departing Mexico back to the US. I believe that your Green Card will also be sufficient there (it certainly would be if you were not a Mexico citizen), however I am not 100% sure of that for Mexican Citizens.