what you are doing there will require 3 biquads. if that was your aim, this way it will of course work to design a filter.
yet you are still ending up with a series of filters of the known standard types. :)
how to use a linear knob or fader to control poles and zeros? no idea.
i think to find musically interesting settings you can stick to using multiple filtergraphs … the zplane isnt really giving you access to something useful.