If you have a food processor, run the potatoes, yellow squash, zucchini, onion, and garlic through it on the grate setting. If you don't have a food processor, you can use a box grater to grate the vegetables.
Squeeze the excess moisture from the vegetables. (Removing the liquid is essential to making crispy hash browns).
Add the seasoned salt and pepper to the vegetables and stir to thoroughly combine.
Add oil to a largest skillet you have. Spread the hash brown mixture evenly over the bottom of the pan.
Cook over a medium high flame until the bottom is crispy, approximately 4 - 6 minutes. Then flip and cook until the other side is crispy, approximately 4 - 6 minutes.