How to measure the rotational speed by using rotary encoder and 1 counter?

I want to measure the rotational speed of a shaft, and I have below hardware:

1, a rotary encoder, with A,B,Z signals output;

2, PCI-E6363 card.

I do konw how to use such a  encoder to measure the rotational angle by using the function

"DAQmxCreateCIAngEncoderChan", but this time I need to measure the speed(rpm), as well as the dirction

of the speed, which means a negative speed represent a CCW rotate direction.

More detail informations:

for the encoder, the A,B signal is 600ppr, and Z signal is 1ppr

the rotatinal speed is in range:　-300 ~ 5000 rpm.

some one suggested me that I can use the "DAQmxCreateCIAngEncoderChan" task to measure the angle firstly

and then do the differential analysis with the angle. but I have to enable the Z index function, and

it's hard to calculate when the shaft speed is fast then 2500rpm.

Anyone can help me on this issue?

Thanks in advance!