words and phrases about level of difficulty

Downhill

The hard work is over (climbing the hill) and the remainder is easy

“Now that we have compiled the numbers for the report, it's downhill from here.”

The opposite is uphill. The easy part is done and the remainder is difficult.

Skate

expend as little energy as possible

“Ebata-san thought he would skate through graduate school but it was more difficult than he had expected.”

No-brainer

Extremely simple decision that requires no debate

“Mika said her decision to work during her pregnancy was a no-brainer.”

Walk in the park

A task that require very little effort

“Yano-san said her previous job was like a walk in the park compared her new position as a supervisor.”

Like pulling teeth

Very difficult, somewhat painful or troublesome

“Getting the accountant to approve additional expenses is like pulling teeth.”