Medellín is 1 hour ahead of Mexico City
Best overlap: 8:00 AM to 5:00 PM in Mexico City is 9:00 AM to 6:00 PM in Medellín.
Shoot for 8:00 AM to 5:00 PM in Mexico City; your Medellín colleagues will see that as 9:00 AM to 6:00 PM. That's a roomy 9 hours of common time each day, so finding a slot that suits everyone is rarely a problem.