Factor y2 + 10z - 10y - yz

Group and factor

group y's with y's and z's with z's

(y²-10y) + (10z-yz)

factor

y (y-10) + z (10-y)

force undistribute - 1

-y (10-y) + z (10-y)

factor

(10-y) (-y+z)

(z-y) (10-y) or

(y-z) (y-10)