I just used an ounce of zest and 3/4 oz coriander in 5 gal of witbier. It tastes amazing. I used whole coriander seeds and used my mortar and pestle to crack them. Cut those in half and I think you'll enjoy your final product
I used the following in an 2.5 gallon extract recipe fermented in a Mr. Beer keg - the bottling wort tasted delicious. Will be able to drink next week.
¼ oz Coriander, crushed (boil 10 min)
½ oz Orange Peel, Sweet (boil 10 min)