Z modulation is PCM 512. S modulation is PCM 1024. There is twice as much resolution with the S than the Z. On large control surfaces with large amounts of deflection the surface will look like it is moving in "steps" with Z modulation. If I'm not mistaken, all Z modulation RX's are single conversion. In my opinion, The "safest" setup is an S PCM 940/945 dual conversion receiver. These RX"s seem to be the most resistant to ECU/pump noise.
Your RX (Z PCM 910???) should be ok---you just won't have as much resolution. Whatever you do, perform a range check with any RX you choose.

I don't understand the quote in the previous post. PPM is FM. PCM is carried on an FM signal. I would imagine that the newer S PCM RX's are better overall besides just the improved resolution. I'm not a JR rep, so I don't know.

FWIW---a buddy of mine has flown his HotSpot with no problems using a Z PCM 910 RX. Kevin