Before retiring to a blissful life of gardening in rural France I was responsible for regulatory compliance in an industry that used chlorine (bleach) as a sanitizing agent at a target rate of 50ppm. Using an 8% solution of bleach (which is stronger than the 5%+/- you buy in the states) that would be approximately 4 or 5 cc diluted in something less than a gallon of water. Your cowboy cleaners used far more in concentration.
Bleach is very effective, it 'kills' everything.
All of the advice has merit. The most important being flush with water...over and over and over.
We also used acetic acid - vinegar (or others) as a neutralizer in releasing waste water but it too requires calculating with known volumes...and as a homeowner you cannot possibly know what that is in soil after the fact.
Flush with water, cut back dead growth, have your attorney write a very nasty letter to the landscape (?) company. They should not be in business.
