Looks like this problem wants you to find bounds (between which x-values) you can find "all possible" zeros. Two simple steps
1. Use the rational root test to find possible zeros.
Possible zeros: x = +/-1, +/-2, +/-3, +/-6
2. Determine from the possible zeros which two x-values are the highest positive and highest negative value. All possible zeros will fall within this "domain" of x-values. In this case, -6 and +6 are the most negative and most positive values, so the upper and lower bounds are (answer expressed in interval notation):
The brackets are closed because -6 and 6 could possibly be zeros to the function.
Hope this was insightful :)