How to make higher order transfer functions stable? or How to Reduce Transfer Function?

I estimate transfer functions from my experimental data using idfrd and tfest, I have two components PZT Amp (21st order system) and PZT Actuator (31st order Plant). Both of my transfer functions are unstable when i check with

is_stable = isstable(tf_Plant);
disp(is_stable)

it's return 0.

instead of posting code here, I am attaching zip file containing matlab and csv files.

How can I reduce my Transfer function order and make them stable? Even, When I check my PZT Amp system with 6th order transfer function it showed unstable (0). I am very new to MATLAB and struggling hard to deal with these higher order systems.

Secondly, I want to use simulink and check step response of my system, It give me following errors,

First error arising from "PZT Transfer Function" block that my indexing is not correct, and when i try to change .Num{:} to () it's give me another error invalid setting ........ for parameter 'Numerator'.

Secondly I try use LTI block to apply step response again I get "An error occurred while running the simulation and the simulation was terminated"

i don't know how to deal with all these problems.