On September 1st, 2024, the LXVI Legislatura del Congreso de la Unión, Mexico’s 66th Congress, convened. It is scheduled to end on August 31st, 2027.
The members-elect were sworn in a few days earlier, on August 29th; they took office September 1st.
Let’s look at the configuration of Congress.
THE CHAMBER OF DEPUTIES
The lower house is the Cámara de Diputados, the Chamber of Deputies, equivalent to the U.S. House of Representatives. It has 500 representatives, each with a 3-year term.
Here are the parties in the Chamber and how many seats each has:
The MORENA Coalition:
MORENA: 257
Green Party: 60
Labor Party: 47
Opposition Parties:
PAN: 71
PRI: 36
Movimiento Ciudadano: 27
PRD: 1
Independent: 1
Note that the MORENA coalition (MORENA/Greens/Labor) has 364 seats out of 500. That’s higher than the 334 seats which would give them a two-thirds super-majority.
The Presidenta de la Cámara de Diputados, equivalent of Speaker of the House in the U.S. Congress, at 94 years of age, is Ifigenia Martinez, for whom Claudia Sheinbaum voted in the recent election. She is a member of the MORENA party:

THE SENATE
The upper house is the Senado, the Senate, equivalent to the U.S. Senate. It has 128 senators. Like those in the U.S., Mexican senators have 6-year terms.
Here are how many senators each party has in the Senate:
The MORENA coalition:
MORENA: 62
Green Party: 14
Labor Party: 9
Opposition Parties
PAN: 22
PRI: 16
Movimiento Ciudadano: 5
The MORENA coalition has 85 senators out of 128, just one seat short of a super-majority. How hard would it be to entice one more senator to jump ship and join the winners?
The leader of the Senate, the Presidente de la Cámara de Senadores, is Gerardo Fernández Noroña, of the Labor Party, a member of the MORENA coalition:

CONCLUSION: This new Congress is overwhelmingly dominated by the MORENA coalition. Both the current president (AMLO) and president-elect (Claudia Sheinbaum) are of the MORENA Party (founded by AMLO).
If the MORENA coalition in the 66th Congress remains united and can pick up one more vote in the Senate, it can pass any law it wants and amend the Mexican Constitution, regardless of how the opposition parties vote.
I hate to learn this latest information on the Mexican government but I certainly appreciate knowing this.