RHP zeros in control systems
When you decouple a MIMO system you turn it into a series of SISO systems. So you transform your system from a single 2 inputs 2 outputs system into two independent SISO systems by having a diagonal matrix. Moving the unstable zero to one of the inputs you can control which output is affected. The result is that only one of the outputs remains decoupled since you transform the diagonal matrix into a triangular matrix.

Using this method you can move the drawbacks around the system. Maybe one of the outputs moves slowly. Hence you don’t need good performance on said output. However you need a fast response on the other output.