To simplify this expression, we need to convert all angles to acute angles and then apply the trigonometric identities.

Given: 2cos²135° + 6sin150° - 4tan0°cos141°

Convert all angles to acute angles:
cos(135°) = -cos(45°) = - √2/2
sin(150°) = sin(30°) = 1/2
tan(0°) = 0
cos(141°) = cos(141°) = -0.8746

Now the expression becomes: 2(-√2/2)² + 6(1/2) - 4(0)(-0.8746)
= 2(2/4) + 3 - 0
= 1 + 3
= 4

Therefore, the simplified expression is 4.