What dose equivalence to use when changing between Z-drugs

A colleague asked about changing a patient’s hypnotic from zolpidem 10 mg at bedtime to a longer-acting “Z-drug” because the zolpidem was working but its effect did not last through the night. Apparently, there was a shortage of zolpidem controlled-release. In any case, lasts only a bit longer than zolpidem immediate release).So, we agreed that…