The greatest common factor is 2z^3.
In order to find the greatest common factor, always start with the coefficient of the lowest term. Let's see what the factors of 14 are.
Factors of 10: 1, 2, 5, 10
Now we look to see which are also factors of the next highest number.
Factors of 14: 1, 2, 7, 14
Only 1 and 2 are similar factors. Since 2 is also a factor of 70, 2 in the coefficient of our greatest common factor.
Next we look for the term with the least number of z's. 14z^3 is the least number of z's. This means we can take out z^3. Giving us the final answer of 2z^3.
