(I) Three nonzero integers x<y<z are in Arithmetic Sequence (in this order).
Determine all possible triplets (x,y,z) that satisfy this equation;
x² + y² = z² - 2x*y*z

(II) With all the other conditions in (I)remaining unaltered, determine all possible triplets that satisfy this equation:
x³+z³=y³+7*y*z