I am assuming you have applied the REST DPH with an appropriate rule you now have the number as an argument of your transaction signature inside your .vsi file.
You will have 2 specific transactions, one specific transaction containing the response for the even number, one for the odd number.
By default the comparison operator for the "number" argument will be equal (=), change that to regex and put the following:
- regex: .*[02468] for the even number transaction
- regex: .*[13579] for the uneven number transaction
Apologies, I do not have the bandwidth to provide screenshots.
Cheers,
DAnny