This is the first spring in my new house, and I'm curious as to what these large shrubs are at the back of my property. They're flourishing in a pretty shady spot, and are deciduous. They're probably 10-12 feet tall, equally as wide, and covered in white blooms. I'm in CT, in zone 6a, and some other plants that are blooming right now are crabapples and lilacs, so this one isn't a real early bloomer. I've attached pictures from a few days ago, one a closeup of leaves/blooms, the other from farther back, attempting to show the overall form and size (the giant thing to the right of my dog).

Any ideas? I've done image searches, tried to identify by leaf-shape and flowers, looked up just about every spring-flowering shrub I could find, and I STILL haven't found this guy!