we have
[tex]14(\sqrt[4]{a^{5} b^{2} c^{4}})-7ac \sqrt[4]{ab^{2}}[/tex]
we know that
[tex]\sqrt[4]{a^{5}}=a \sqrt[4]{a}[/tex]
[tex]\sqrt[4]{c^{4}}=c[/tex]
substitute
[tex]14(\sqrt[4]{a^{5} b^{2} c^{4}})-7ac \sqrt[4]{ab^{2}}=14ac(\sqrt[4]{a b^{2}})-7ac \sqrt[4]{ab^{2}}\\ \\=(14ac-7ac) \sqrt[4]{ab^{2}}\\ \\=7ac \sqrt[4]{ab^{2}}[/tex]
therefore
the answer is
[tex]7ac \sqrt[4]{ab^{2}}[/tex]
