A high risk / high reward operation

or

To achieve something partially through intense skill and partially through luck

or

Not only do you have to be lucky in achieving the right outcome, but you also have to avoid the wrong ones on the way.

Urban Dictionary

The term originates from craps. It means skill and luck to achieve an outcome.

rolling 2 3s equaling 6

“hard” = “against the odds”? Less likely to roll 2 3’s than a 4 and and a 2, or a 1 and a 5?

Number six in french,czech,polish,german,slovakia,italy,english,dutch,languages start an letter s.I mean if you say six or if you write it allways is there s.This is easy to remember when some one learn languagesnumber six.