Virtual corrections to $gg\to ZH$ in the high-energy and large-$m_t$ limits

We compute the next-to-leading order virtual corrections to the partonic cross-section of the process $gg\to ZH$, in the high-energy and large-$m_t$ limits. We use Pad'e approximants to increase the radius of convergence of the high-energy expansion in $m_t^2\mathrm{/}s$, $m_t^2\mathrm{/}t$ and $m_t^2\mathrm{/}u$ and show that precise results can be obtained down to energies which are fairly close to the top quark pair threshold. We present results both for the form factors and the next-to-leading order virtual cross-section.