Could you please help me solving this complicated (or maybe just complicated looking limit problem?

$\displaystyle \lim_{\displaystyle x \to 0+} \frac{\displaystyle\int_{0}^{x}\left(\int_{0}^{t}\ sqrt{\displaystyle1+z^4}\mathrm{d}z\right) \mathrm{d}t}{\displaystyle\int_{0}^{x}\left(\int_{ 0}^{t}\sqrt{\displaystyle1+z^6}\mathrm{d}z\right) \mathrm{d}t} $

Any help would be appreciated!