These matters are both very difficult and (except for strict Little Raft Buddhists, who are interested only in the relief of suffering, not in metaphysics) very important.
These are very difficult and crucial.
These matters are of little importance.
a person working on an engine
Buying
A child  by a sewer drain cries
A woman in white shirt play guitar to a woman in a white shirt.
But an extra smoke stack is usually unnecessary.
Two people sky dive from a submarine.