Correct. Neither of these pairs consists of like terms. Although they have the same variables, $\displaystyle{3}{{x}}^{{2}}{{y}}^{{3}}{{z}}^{{4}}\usepackage{cmbright}\Huge\$ and $\displaystyle{3}{{x}}^{{2}}{{y}}^{{6}}{{z}}^{{4}}\usepackage{cmbright}\Huge\$ have a different exponent for y. In the other pair, $\displaystyle-{3}{q}{{z}}^{{5}}{y}\usepackage{cmbright}\Huge\$ and $\displaystyle{92}{q}{{z}}^{{5}}{x}\usepackage{cmbright}\Huge\$ have the same exponents but different variables.