Glad you asked. The Zone Theory of Child Development claims to be based on Vygotsky’s sociocultural theory (including his zone of proximal development, or ZPD), but it’s framed in terms of learning-as-attainment, which is inconsistent with Vygotsky’s work. In short: ZPD is green. ZPCD is red. Check out the (green) entry on “socio-cultural theory” for the real Vygotsky.