Mix sausage, zucchini, and red pepper flakes in a bowl. Form mixture into 10 patties.
Cook patties in a skillet over medium heat until no longer pink in the center, 5 to 7 minutes per side. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
Spread cream cheese over English muffins; arrange cooked patties and spinach on top.