Prescribed mass standing waves for Schrödinger-Maxwell equations with combined nonlinearities

In the present paper, we study the following Schrödinger-Maxwell equation with combined nonlinearities \begin{align*} \displaystyle - Δu+λu+ \left(|x|^{-1}\ast |u|^2\right)u =|u|^{p-2}u +μ|u|^{q-2}u\quad $\text{in}$ \ $\mathbb{R}$^3 \quad \quad $\text{and}$\quad \quad \int_{$\mathbb{R}$^3}|u|^2dx=a^2, \end{align*} where $a>0$, $\mu \in \mathbb{R}$, $2<q\le \frac{10}{3}\le p<6$ with $q\mathrm{\ne }p$, $\ast$ denotes the convolution and $\lambda \in \mathbb{R}$ appears as a Lagrange multiplier. Under some mild assumptions on $a$ and $\mu$, we prove some existence, nonexistence and multiplicity of normalized solution to the above equation. Moreover, the asymptotic behavior of normalized solutions is verified as $\mu \to 0$ and $q\to \frac{10}{3}$, and the stability/instability of the corresponding standing waves to the related time-dependent problem is also discussed.