2(√36:√9)-(2√12:√3)=

2(√36 ÷ √9) - (2√12 ÷ √3)
= 2(√36 ÷ √9 = √4) - (2 × √12 ÷ √3)
= 2√4 - (2 × √4)
= 2√4 - 2√4
= 0

2(6:3) - ( 2 x 2 √3 : √3)
= (2 x 2 ) -(2x2)
= 0