I think the two are very similar.

All books of his are great books

You may also want to look at Ross Greene's books. The Explosive Child helped me a great deal with mine, even though our issues aren't as extreme as the ones used as examples in the book.

I use Kazdin as shorthand for "The Kazdin Method" (just because it's the one I've read). FWIW, it seems applicable to a broad range of kids, not just typically "defiant" ones.

Is it "The Kadzin method for parenting the defiant child" or "The everyday parenting toolkit?" This is for a 5-year-old with low frustration tolerance, anxiety and likely ADHD.