I have no personal experience with this, but a few possibilities occur to me:
Maybe you could move the nestboxes higher? If the chickens can fly to a perch and then step into the nestboxes, but the dogs cannot, that might solve your problem. (Of course, that only works for some styles of coop, for some kinds of chickens, and for some kinds of dogs. Heavy chickens may not fly any higher than an athletic dog can jump.)
Hot peppers burn the tongues of mammals (including dogs) but not birds (like chickens.) You might be able to put cayenne pepper or something like that in the nestboxes. Especially if it sticks to the wet bloom when the eggs are laid, it might deter the dogs (or it might not.)
You could try letting the dogs out only when you can supervise, and reprimand the dogs each time they try to go into the chicken coop. (Time consuming, probably works better with some dogs than others.)
You could try making a hole in each end of an egg, blowing out the insides, then filling the shell with hot sauce or something else the dogs do not like. Then put that "egg" in the nestbox and let the dogs have it. (I've read of this, and it sounds clever, but I'm sure some dogs would just learn to check for eggs that smell normal vs. different.)
Maybe consider an invisible fence (the kind where the dog wears a collar that shocks it), set up right around the chicken coop to keep the dogs out.
Or an electric fence around the chicken coop, if you can arrange a height that lets chickens in but zaps dogs.
Many eggs tend to get laid in the morning, so you may be able to keep the chickens penned until most eggs have been laid, then collect the eggs, then let the chickens and the dogs out for the rest of the day. This would not re-train the dogs, but would let you get most of the eggs.