The numerical coefficients of given numerical are 42 and 63.

Greatest common factor of 42, 63 is 21.

Common literals appearing in given numerical are x, y and z

Smallest power of x in two monomials = 2

Smallest power of y in two monomials = 1

Smallest power of z in two monomials = 1

Monomials of common literals with smallest power= x²yz

Hence, the greatest common factor = 21x²yz