Scenario:
Humans have assimilated and became space faring (on a level equivalent to the movie Avatar) and are seeking new resources to fuel our expansion and reduce strain on Earth's dwindling resources.
Initial peace is established between the colonists and the nation-states of Equestria, but quickly breaks down as human colonies expand to begin to ravage the land. At the time of declaration of open conflict, humans are still a minority, but are rapidly gaining ground. Given technology, humans can reach equestria in six months
Belligerents:
Republic of Earth and human colonial militias vs an alliance between Equestria, the Crystal Empire, and the Gryffons.
Battleground:
Equestrian kingdoms, Gryffon kingdom, space (orbital bombardment).
Initial Strength:
Humans: 2.2 million colonists, garrison of 85,000 ROE troops, 100 tanks and armored vehicles, 150 combat aircraft (both space and atmospheric capabilities). Food and water stores for six years, with full recycling systems and new crop production. Electric from renewable sources.
Equestria's coalition:
Anything that's been featured in FiM.

How would it play out?