How would you calculate the input and output impedance of this amplifier?
If Q1 was an NPN transistor (as I suspect it should be) the input impedance at mid-band (no appreciable extra impedance due to C1) is approximately R1 || R2 and, if you wanted to be pedantic you would have that impedance in parallel with \$\beta\cdot\$R4 where \$\beta\$ is the gain of Q1.

The output impedance (mid band hence ignoring C2) is dependant on the current flowing through Q2 and Q3. If that current is small then the internal \$r_E\$ might be higher than R5 or R6 and will sway things. If you ignored \$r_E\$ then on positive half cycles the output impedance is R5 and on negative half-cycles it is R6. If R = R5 = R6 then the output impedance is approximately R.

The above assumes that RL isn't connected.

I have also assumed that the circuit is for an audio amplifier with mid-band frequency around 1 kHz.