Unless you are using a dual core system real multi-theatding does not exsist.

But what dou you need?
To read 2 values within a determined time interval?

If you need teh 2 values at exact the same time there is a trick:

1) read sensor 1 (value a)
2) read sensor 2
3) read sensor 1 (value b)
4) interpolate sensor 1 values to the right time.

If the time between measurements is not to long one can assume a linear realtion between value a and b.

But probably this is way to difficult, normally a 1 or 2 ms offset is not that much of a problem (with good programming 10 us is also possible)

regards