Combine like terms
the number two means squared and the number three means cubed
z2+z+4z3+4z2

Lets write this out:-

z² + z + 4z³ + 4z²

z² will become 1z² because when ever there is a varaible, and before it there is NO coefficient the coefficient automatically becomes 1. Same is with z. z will be come 1z.

Lets write it out again:-

1z² + 1z + 4z³ + 4z²

Combine like terms:- 

1z² + 1z + 4z³ + 4z²
(1 + 4)z² = 5z²
1z + 5z² + 4z³

So, when combining like terms in z² + z + 4z³ + 4z² the answer is
1z + 5z² + 4z³.

Hope I helped ya!! xD