Hi Viking,
For the sentences below, I am strictly speaking about if you use them as a statement sentence beginning with "IT".
"It difficult to do", is not correct English.
"It is difficult to do", is correct.
Firstly, there needs to be a subject, so in the case of the correct sentence, the subject is "it". In order to describe "it", you need to use the word is/was etc.
The key is the use of the word "is". This is because in English, something is, or was, or is going to be difficult, so it needs a tense to place it.
>>>>>>HOWEVER>>>>>>
when it is the second half of a sentence, for example:
"I find it difficult to say sorry."
This is okay because you now have a subject of "I". So, who found it difficult - "I' did…….and what did you find difficult……."it".
In the second part to your question, I believe that both the statement are correct.
It is easy to do.
It is difficult to do.
Both are correct, although perhaps not how a Native English speaker would say it. Native speakers tend to shorten the phrase "it is" to …….it's
They would often use another adjective to describe "how" difficult too, for example:
- very difficult
- quite difficult
- extremely difficult
- rather difficult
- immensely diffucult
- mildly difficult
so you would say, for example: It's rather difficult.
Hope this helps