Window infill/ rendering over different substrates

Hi everyone

I’ve recently had two new windows installed both are 2400 long.

The height of the new windows means they sit 150mm below the height of the eaves.

We are looking at getting our house rendered shortly and are wanting to infill these gaps.

My question is that if this gap is filled in with a hebel/ foam product will they be able to render between the brick work and the infill or will it require an expansion joint between the two substrates, or is it even possible to render over the two different substrates without cracking issues??

Thanks