These are just examples of the sorts of answers you might think of

X → Y : Microwave radiation causes cancer (there is no reliable evidence that this is actually the case, and a great deal of evidence that there is no simple link).

Y → X : I can't think of anything plausible here!

Z → X & Y : Antennae are placed where land is cheap, so they tend to be surrounded by poor housing. People in poor housing are less likely to have nutritionally adequate diets, which predisposes them to cancer. (Z is the cheap land and associated poor housing).

Similar arguments could be made about the alleged link between mobile phone use and brain tumours. In both of these cases, even the evidence for correlation (let alone causality) is poor. It pays to keep an open mind, but not one so open that your brains fall out.