Question

why do my zuccini plant leaves have holes

Answer 1

It sounds to me like some type of pest.  Examine the leaves very closely, some pests, particularly caterpillars are very small and difficult to detect. If you do find caterpillars, you can use thurcide on the plant. As always, mix according to the directions and spray both sides of the leaves and around the plant as well.  It is best to do this in the early evening because exposure to early day light may cause spray burn. Thuricide only works against leaf eating caterpillars.  It is harmless to most everything else unless there is a specific allergy to the ingredients.

Answer 2

after the sun goes down mix up 1 teasp liquid hand soap & 1 qt of water spray on under and the ground.  Some bugs only come out at night time and have a party eating of of your garden.......they won't like the soapy bath.  This is the safest method....and you can use it  after it rains.....to keep them at bey.