hard yards
mission impossible
heavy lifting
job
laboring oar
grind
dys-
mountain
over the river and through the woods
scut work
mahi
task
snorter
challenge
pull teeth
inadequate
order of business
unequal
arduous
difficulty level
long row to hoe
brain-teaser
enigma
riddle
conundrum
dare
defy
doddle
proposition
queer someone's pitch
hard going
throe
hack
tasky
mean
waltz
time-consuming
hay ride
skittish
lightning in a bottle
rush job
unwieldy
chore
boil the ocean
chapter
ambitious
challengeful
mountain to climb
backbreaker
Sisyphean labour