Usually you can get all that from hops and yeast esters.
But if you do want to use fruit you can.
If you puree peel and all I recommend the addition to go in after the boil on the chill at about 170°F, 32-64oz is a good amount to use on 5 gallon test batches.
If you use zest. I recommend washing the citrus very well and use a potato peeler to remove the zest and not the white bitter part. Add the zest to secondary fermentor when alcohol is close to it's highest point. Zest from a few fruit goes a long ways.
You can also do a zest tincture. Soak zest in a clean high alcohol vodka 100 proof. Use a vodka that has a plain flavor. This tincture can be added post fermentation or in secondary. This method gives more piece of mind to sanitation than raw zest.
Volumes and times really isn't an exact science when it come to fruit because they differ from fruit to fruit, crop to crop, year to year.