Rinzai is telling us to stop thinking and to give ourselves to our ordinary daily activities. Give yourself to whatever you are doing wholeheartedly.
As for Zazen, don't see that as something special - again, please listen to Master Rinzai's kind advice. It's not the lack of Zazen that is your problem, it's the thinking! I'm sure an hour or so a day would be quite enough lol.
Hope that helps,
How does this tally with the Sutra of Perfect Enlightenment
which speaks of four maladies people suffer from who want to engage with Buddhism? Two of the maladies are stopping thought and naturalism, i.e., letting things follow their natural course.
To give a more complete answer - and this is purely based on my experience - the intellect chops reality into this and that and from what I could work out the purpose of all the things we do in practice is to de-clutch from the thinking mind, release ourselves from its iron grip, and see things straight for the first time . While anyone is chasing ideas around they cannot de-clutch, and are lost in the wisteria tangle of thought and are literally chasing ghosts or reflections that appear on the surface of the mind. However, once released, you can see the thinking for what it is, and that the "I" is the ghost in the machine, just another idea swirling round the mental apparatus.
Once de-clutched from the mind you enter a place known as the 'Original Face'. It all sounds a bit strange, but that's what happens! In the Rinzai system this comes just before the passing of the first Koan - which happens as soon as you can figure out how to become the Original Face in front of the teacher. Then all the other satellite Koans and ongoing practice deepen that insight and get you operating out of the Original Face, (or 'Mu" or the "one hand" - whatever you like to call it) rather than out of the intellect. You can still think, obviously, but it just doesn't have the hold on you it once did. At some point there is a merger or something, and then you are heading towards the more mysterious end of the Ox Herding pictures.
I'm not a zen master or anything, (and my teacher would laugh his ass off if he thought that I was trying to give out advice because I'm still a beginner) but I have done a years monastic training in the traditional line and so that is what I experienced, and this stepping back has helped me many times in ordinary life. However, have I fallen back, yes, because it's very difficult to not slip back into taking the mind 100% seriously!