"In brief, it's very difficult to think of how intellect can be wasted the way intelligence can be. Therefore intellect = intelligence + wisdom"

If a person has a somewhat high intelligence, but seldom uses it to think deeply, then he is wasting his intelligence. He has intelligence, but does not use it.

If he thinks deeply about things that are silly, he is wasting his intellect.

OTOH, he might have a high intelligence (of the trivial type), but nevertheless think poorly when he attempts to think deeply.

I consider wisdom a kind of intelligence - one of course which has a synergy with the other kinds. I'm not sure of an actual equation, but it might go something like this:

intellect = intelligence + interest + diligence + discipline

Implicit in the formulation of intelligence would be judgement or discernment, experience (and learning from it), and maybe a bit of art, but I'm not sure.