factor 14x^2y^2z + 21x^3y^7z^4

The common factor in both terms is x^2y^2z.

If we factor out x^2y^2z from both terms, we get:

14x^2y^2z + 21x^3y^7z^4
= x^2y^2z(14 + 21x)y^5z^3

Therefore, the factored form of 14x^2y^2z + 21x^3y^7z^4 is x^2y^2z(14 + 21x)y^5z^3.