[Baertram]

As shown above the code should look like this:

ZO_PreHook("TogglePlayerWield", function() 
    d("TogglePlayerWield was used")
    return false -- reutn false to run original function code of TogglePlayerWield afterwards!
end

ZO_PreHook(objectTable, existingFunctionName, hookFunction)

objectTable: The name of an object (e.g. SMITHING) or if it is the global namespace (_G) you can just pass the function name existingFunctionName without the objectTable.

existingFunctionName: The name of the function you'd like to preHook, in string quotes " "

hookFunction: Your definded hook function or an anonymouse function within the prehook like shown above in my example code.

So your code should look like this e.g.

ZO_PreHook("TogglePlayerWield", function() 
    myAddon.TogglePlayerWield()
    return false -- return false to run original function code of TogglePlayerWield afterwards!
end)

This is the same:

ZO_PreHook(_G, "TogglePlayerWield", function() 
    myAddon.TogglePlayerWield()
    return false -- return false to run original function code of TogglePlayerWield afterwards!
end)