It's interesting that FindInstance only finds 1 solution, when there are many solutions, these are just the first few
62616840 , {{y->62616840,z->62616840}}
62616826 , {{y->131915080,z->10050766},{y->131915080,z->52566060}}
62616812 , {{y->92362065,z->2647718},{y->92362065,z->59969094}}
62616758 , {{y->122326338,z->7684682},{y->122326338,z->54932076}}
62616688 , {{y->25532718,z->63478756},{y->27384238,z->63494884},{y->35232450,z->63494884},{y->37083970,z->63478756},{y->96758670,z->3214116},{y->96758670,z->59402572}}
Maybe its because there's too many solutions.