2.123. $2 \sqrt{40 \sqrt{12}}+3 \sqrt{5 \sqrt{48}}-2 \sqrt[4]{75}-4 \sqrt{15 \sqrt{27}}$.
Solution.

$$
\begin{aligned}
& 2 \sqrt{40 \sqrt{12}}+3 \sqrt{5 \sqrt{48}}-2 \sqrt[4]{75}-4 \sqrt{15 \sqrt{27}}= \\
& =2 \sqrt{40 \sqrt{4 \cdot 3}}+3 \sqrt{5 \sqrt{16 \cdot 3}}-2 \sqrt[4]{25 \cdot 3}-4 \sqrt{15 \sqrt{9 \cdot 3}}= \\
& =2 \sqrt{40 \cdot 2 \sqrt{3}}+3 \sqrt{5 \cdot 4 \sqrt{3}}-2 \sqrt{\sqrt{25 \cdot 3}}-4 \sqrt{15 \cdot 3 \sqrt{3}}= \\
& =2 \sqrt{80 \sqrt{3}}+3 \cdot 2 \sqrt{5 \sqrt{3}}-2 \sqrt{5 \sqrt{3}}-4 \sqrt{45 \sqrt{3}}= \\
& =2 \sqrt{16 \cdot 5 \sqrt{3}}+6 \sqrt{5 \sqrt{3}}-2 \sqrt{5 \sqrt{3}}-4 \sqrt{9 \cdot 5 \sqrt{3}}= \\
& =2 \cdot 4 \sqrt{5 \sqrt{3}}+6 \sqrt{5 \sqrt{3}}-2 \sqrt{5 \sqrt{3}}-4 \cdot 3 \sqrt{5 \sqrt{3}}= \\
& =8 \sqrt{5 \sqrt{3}}+6 \sqrt{5 \sqrt{3}}-2 \sqrt{5 \sqrt{3}}-12 \sqrt{5 \sqrt{3}}=14 \sqrt{5 \sqrt{3}}-14 \sqrt{5 \sqrt{3}}=0 .
\end{aligned}
$$

Answer: 0.