User blog comment:Mh314159/A new approach, and a typography question/@comment-34422464-20190701005428/@comment-35470197-20190701032006

Does the following include what you need? (Please delete the spaces between the backslashes and the braces.)

\ ( \iint \int_{\vartheta}^{\varphi} \frac{\textrm{roman font} \times italic font + \bf{bold font}}{\sin(\cos(\tan(x)))} \cdot \overline{v} d \underline{\tau} d \Phi \underbrace{d \chi \cdots d \omega}_{\to \uparrow \leftarrow \downarrow \stackrel{f}{\Rightarrow}} \ )

It will be displayed in the following way:

\(\iint \int_{\vartheta}^{\varphi} \frac{\textrm{roman font} \times italic font + \bf{bold font}}{\sin(\cos(\tan(x)))} \cdot \overline{v} d \underline{\tau} d \Phi \underbrace{d \chi \cdots d \omega}_{\to \uparrow \leftarrow \downarrow \stackrel{f}{\Rightarrow}}\)

You can also use \begin{eqnarray*} \end{eqnarray*} command.