Historically, copper and zinc products used to treat dairy cattle hooves in footbaths have been lumped together in much of the literature as it relates to soil toxicity. In reality, these two metal micro-nutrients are very different when it comes to soil toxicity risk.
The following link provides the research to support why it is unwise to consider copper and zinc toxicity risks to be perceived as equal.
Hoof-Zink® reduces soil toxicity risk