intellectual understanding is one thing. it is important. zazen goes beyond this. i think to understand intellectual understanding is to know its limitations and as long as you are not deluded into mistaking it for the way, it is healthy and advantageous.
however zazen goes beyond this. and you can not be zen if you do not let go of the conscious thought that is merely a small part of the dharma. to go beyond is to be in the present moment fully. it is knowing that everything is perfect as it is and there is no need to change a thing, no matter how it is. this is difficult, because we think in terms of good or bad.
these are opinions and nothing more than that. they are not absolute. it is the ego that controls this attitude, which is why it is important, vital, to see that the ego is merely a manifestation of the present moment and is in no position to control or decide what is good or bad. how could it, if it is it?