Input impedance of AD8220 with ADG1209

In my previous design, AD8220 was chosen because of the requirement of the extremely high input impedance. However, I need to modify the circuit design by adding a demultiplexer to perform a 1 to 4 switch function and ADG1209 seems suitable for my design.

However, if I add an ADG1209 after AD8220, how will it affect the input impedance of the system?

I need to maintain a high input impedance.

I attach my AD8220 circuit design in this post. ADG1209 will be added after R11 and R12.