Zero Forcing Equalizer in ISI channel
Your channel has 3 taps, your EQ has 9 taps which means that your cascaded response has 11 taps. You only force the middle 9 taps of the response to be a unit impulse. If you convolve the channel with your EQ, you see that the middle is indeed a unit impulse but the first and the last sample are very non-zero.

The actual inverse your channel would be an IIR filter. To approximate this with an FIR filter, you need to have a fairly well behaved channel and spent a fair amount of FIR taps. Your channel is NOT well behaved since it got zeros on the unit circle, which means it's not invertible.