Combine like terms.

z³ + y² + 2z³ + 5y²

!

Z³ + y² + 2z³ + 5y²

(1 + 2)z³ = 3z³
(1 + 5)y² = 6y²

z³ + y² + 2z³ + 5y² 
Combined like terms:-
3z³ + 6y²

To combine like terms we will write our expression again:-

z³ + y² + 2z² + 5y²

z³ will become 1z³ because whenever there is a variable WITHOUT a coefficient before it the coefficient AUTOMATICALLY becomes a 1. Same is with y², it will become 1y². Now lets write it out again and then combine like terms.

1z³ + 1y² + 2z³ + 5y²

Identify Like Terms:-

1z³ + 1y² + 2z³ + 5y²
1z³ + 1y² + 2z³ + 5y²

1y² + 5y² = (1 + 5)y² = 6y²
1z³ + 2z³ = (1 + 2)z³ = 3z²

Lets write out our combined like terms:-

3z² + 6y²

So, z³ + y² + 2z³ ³+ 5y² combined like terms will be 3z² + 6y².

Hope I helped ya!! xD