The part of the sentence "it is hard to emphasize" is correct and usable in written English.
You can use it to express the difficulty in conveying the importance of something. For example, "It is hard to emphasize how essential kindness is in today's world."
"It's hard to emphasize how special baseball is in Goffstown".
It's hard to emphasize the radical quality of Bamford's creation, but it's no surprise that it takes something of a sales pitch.
Nonetheless, it's hard to emphasize how helpful and important studying abroad has been, for helping to shape the way I see the world and for keeping me eager to learn more.
It's hard to emphasize just how formative those war movies were for so many of us, especially if you add in the cheap, all-green sets of World War II toy soldiers with which we reenacted movie versions of our fathers' war on our floors and, of course, the sticks, and later toy guns, with which we so gloriously shot down "Japs" and "Nazis" in any park or backyard.
This can very easily be the ultimate limitation on amplifier linearity, and it is hard to over-emphasize its importance.
Fortune indeed favors the prepared mind, and it is hard to over-emphasize the intellectual journey required before the very question of the naturalness of a flat universe could even be discussed.
"You know, it is hard to step back and de-emphasize it," he said.
"While I am gratified by the test results released today for fourth and eighth graders in New York City, I must emphasize that it is hard to tell the true significance of any one set of results in isolation," the chancellor said in a statement.
Our discussion emphasizes that it is hard to choose an optimal polynomial recovery strategy, mainly due to the fact that one can either optimize the decoding time or the success probability but not both (unless a predefined trade-off between the two criteria can be selected).
It is hard to overestimate its importance.
