Start with
[tex]z-8+4z=4-2z[/tex]
Simplify the left hand side by summing like terms:
[tex]5z-8=4-2z[/tex]
Add 2z to both sides:
[tex]7z-8=4[/tex]
Add 8 to both sides:
[tex]7z=12[/tex]
Divide both sides by 7:
[tex]z=\dfrac{12}{7}[/tex]
