Heat oven for at least 20 minutes before baking at 350℉. Slightly mash the ripe bananas with a fork or potato masher.
Mix mashed banana and sour cream together until smooth. Then add in eggs, lemon zest and vanilla. Whisk until very smooth and almost lump free. It will be a loose liquid at this stage.
In a bowl of a stand mixer with a paddle attachment mix flour, sugar, baking soda, baking powder, and salt for one minute.
Add softened butter into flour mixture, along with half of the liquid mixture. After 30 seconds of mixing, add the other half of liquid mixture.
Once the entire batter is well mixed, add the chocolate chips and mix for another 30 seconds.
Using a large cookie scoop, scoop batter into lined muffin tins. The muffins should be filled to the top of the pan, but not overfilled, about two scoops to each liner.
Bake muffins in oven for 25-30 minutes, rotating the pans halfway through. The muffins are done when a toothpick comes out clean.