case class Distance(zip: String, id_5: Array[Int])
val dist = Seq(Distance("72712",Array(72713,72714,72715)))
val distDS=dist.toDS()

case class Customer (cust_id: Int, id: String)
val c = Seq(Customer(1,"72713"),Customer(2,"72714"),Customer(3,"72720"))
val custDS = c.toDS()

val res = distDS.joinWith(custDS,distDS.col("id_5"(??????)) === custDS.col("id"))`

import org.apache.spark.sql.functions.expr

distDS.joinWith(custDS, expr("array_contains(id_5, cust_id)"))