Hi @Gaetinox welcome to the community.
Check out this thread for a discussion aroung this subject. The bottom line is that support for external controllers is not baked into Zynthian control at sufficiently low level and some significant changes need to be made to the code to enable this. Although this is desirable it is not currently required to support the official hardware and hence is low urgency. The code that needs to be touched for this is complex (or at least a bit confusing) and critical for Zynthian operation hence the community who want the change has so far failed to advance this. I have taken a look at this many times but it is a lot of pain for limited gain and I have not yet managed to change things.
There is a general agreement that this should be done but finding the time to do it is proving challenging. Even if a community member was willing and able to make the changes it would require substantial effort from core developers and project lead because there are some fundamental design elements that need to be considered and to expoe maximum benefit these decisions need to be considered carefully by core team members.
Sorry - long winded way to say that there is currently limitations on what is possible. You can drive many aspects of Zynthian via MIDI but there are some core elements that you cannot.