זה = masculine. זאת/זו = feminine.
you can use
זאת OR זו
for feminine words, it doesn't really matter what you choose.
bira (beer) is a feminine noun, therefor - zot ha'bira shelanu.
notice - in spoken hebrew, many native speakers say "ze" both for masculine and feminine words, and would say "ze ha'bira shelanu". while it is grammatically wrong, still many people use only the masculine form.