It has been suggested that the Z-mode instability driven by energetic electrons with a loss-cone type velocity distribution is one candidate process behind the continuum and zebra pattern of solar type-IV radio bursts. Both the temperature of background plasma ($T_0$) and the energy of energetic electrons ($v_e$) are considered to be important to the variation of the maximum growth rate ($gamma_{max}$). Here we present a detailed parameter study on the effect of $T_0$ and $v_e$, within a regime of the frequency ratio ($10 leq frac{omega_{pe}}{Omega_{ce}} leq 30$). In addition to $gamma_{max}$, we also analyze the effect on the corresponding wave frequency ($omega^r_{max}$) and propagation angle ($theta_{max}$). We find that (1) $gamma_{max}$ in-general decreases with increasing $v_e$, while its variation with $T_0$ is more complex depending on the exact value of $v_e$; (2) with increasing $T_0$ and $v_e$, $omega^r_{max}$ presents step-wise profiles with jumps separated by gradual or very-weak variations, and due to the warm-plasma effect on the wave dispersion relation $omega^r_{max}$ can vary within the hybrid band (the harmonic band containing the upper hybrid frequency) and the band higher; (3) the propagation is either perpendicular or quasi-perpendicular, and $theta_{max}$ presents variations in line with those of $omega^r_{max}$, as constrained by the resonance condition. We also examine the profiles of $gamma_{max}$ with $frac{omega_{pe}}{Omega_{ce}}$ for different combinations of $T_0$ and $v_e$ to clarify some earlier calculations which show inconsistent results.
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