If zero lies between a and d, give one set of possible values for a, b, c, and d.
Please note that there can be many possible sets for this scenario.
Let us explore one of the possible sets for the values a, b, c and d.
The important thing here is "zero lies between a and d"
Let zero be in the middle of b and c (which is already between a and d so the condition is satisfied)
Then the number line becomes
As you can see, one of the possible sets for the values a, b, c, and d is
a = -4
b = -1
c = 1
d = 4
Please note that you can take 0 at any point between a and d and it would still be correct.
Another example
As you can see, one of the possible sets for the values a, b, c, and d is
a = -5
b = -2
c = 0
d = 3
The zero is still between a and d so the condition is satisfied.