In a large pot, heat the oil over medium-high heat. Add the ground beef, and cook until browned, about 5-8 minutes. Drain off excess fat.
To the pot, add all other ingredients except for last three (squash/zucchini, cilantro and epazote leaves). Be sure to include the can liquid when adding the black beans- it's yummy.
Bring mixture to a boil, then decrease heat to very low & simmer uncovered for 2-3 hours. Try to mix the chili every 15-30 minutes, especially near the end of the cooking time. Adjust for seasoning near the end as well.
Add the squash/zucchini, stir and cook for a further 15-20 minutes, or until the vegetables are cooked through. When done, remove from heat, then stir in the cilantro and epazote leaves.
Serve with tortilla chips and top with yummy things like queso fresco, cotija cheese or Mexican crema.