\[ y'(x)^6-(y(x)-a)^4 (y(x)-b)^3=0 \] ✓ Mathematica : cpu = 1.05915 (sec), leaf count = 569
\[\left \{\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1-i x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1+i x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1-\sqrt [6]{-1} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1+\sqrt [6]{-1} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1-(-1)^{5/6} x\right ]\right \},\left \{y(x)\to \text {InverseFunction}\left [-\frac {\sqrt [3]{a-\text {$\#$1}} \sqrt {\frac {\text {$\#$1}-b}{a-b}} B_{\frac {a-\text {$\#$1}}{a-b}}\left (\frac {1}{3},\frac {1}{2}\right )}{\sqrt {b-\text {$\#$1}} \sqrt [3]{\frac {a-\text {$\#$1}}{a-b}}}\& \right ]\left [c_1+(-1)^{5/6} x\right ]\right \}\right \}\] ✓ Maple : cpu = 0.359 (sec), leaf count = 250
\[ \left \{ x-\int ^{y \left ( x \right ) }\!{\frac {1}{\sqrt [6]{ \left ( {\it \_a}-a \right ) ^{4} \left ( {\it \_a}-b \right ) ^{3}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{\frac {-2\,i}{-\sqrt {3}+i}{\frac {1}{\sqrt [6]{- \left ( -{\it \_a}+a \right ) ^{4} \left ( -{\it \_a}+b \right ) ^{3}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{\frac {-2\,i}{\sqrt {3}+i}{\frac {1}{\sqrt [6]{- \left ( -{\it \_a}+a \right ) ^{4} \left ( -{\it \_a}+b \right ) ^{3}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{\frac {2\,i}{-\sqrt {3}+i}{\frac {1}{\sqrt [6]{- \left ( -{\it \_a}+a \right ) ^{4} \left ( -{\it \_a}+b \right ) ^{3}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!{\frac {2\,i}{\sqrt {3}+i}{\frac {1}{\sqrt [6]{- \left ( -{\it \_a}+a \right ) ^{4} \left ( -{\it \_a}+b \right ) ^{3}}}}}{d{\it \_a}}-{\it \_C1}=0,x-\int ^{y \left ( x \right ) }\!-{\frac {1}{\sqrt [6]{- \left ( -{\it \_a}+a \right ) ^{4} \left ( -{\it \_a}+b \right ) ^{3}}}}{d{\it \_a}}-{\it \_C1}=0,y \left ( x \right ) =a,y \left ( x \right ) =b \right \} \]