R Studio Shiny zoom subapplication

Question

I have a Shiny "Sub"App called "Bayes Formel" in my Main App

Main App with Sub App "BayesFormel"

uimain <- shinyUI( 

BayesFormel <- shiny::shinyAppFile( 
appFile= 'subdir/BayesFormel.R', options=list( width="100%", height=550))
)
servermain <- function(input, output, session) {
}
shinyApp(ui = uimain, server = servermain)

I'm looking for a way to zoom in and zoom out the subapp NOT changing width and height (otherwise I get scrollbars what I don't want)

I've tried tags$style("body { transform: scale(0.5, 0.5); }") but then it leave white space around, from the "original" width and height

Any ideas how to solve that problem? Thanks!!!