The inequality can be rewritten as: $\displaystyle{2}{z}+{4}\ge{8}\usepackage{cmbright}\Huge\$ or $\displaystyle{2}{z}+{4}\le-{8}\usepackage{cmbright}\Huge\$

Subtract 4 from both sides of both inequalities: $\displaystyle{2}{z}\ge{4}\usepackage{cmbright}\Huge\$ or $\displaystyle{2}{z}\le-{12}\usepackage{cmbright}\Huge\$

Divide both sides of both inequalities by 2: $\displaystyle{z}\ge{2}\usepackage{cmbright}\Huge\$ or $\displaystyle{z}\le-{6}\usepackage{cmbright}\Huge\$