simplified things?

Jenkinsfile

@@ -3,7 +3,6 @@ pipeline {
   
   environment {
     DB_NAME = 'url_shortener.db'
-    ZIP_FILE = ''
   }
   stages {
     stage('Init') {
@@ -44,9 +43,6 @@ pipeline {
     }
     stage('Build production deliverable') {
       steps {
-        script {
-          env.ZIP_FILE=sh(script: 'echo "url-shortener_$(date "+%Y-%m-%d_%H-%M-%S").tgz"', returnStdout: true)
-        }
         catchError(buildResult: 'FAILURE', stageResult: 'FAILURE') {
           sh ''' #!/usr/local/bin/bash
             ZIP_FILE="url-shortener_$(date "+%Y-%m-%d_%H-%M-%S").tgz"
@@ -57,17 +53,17 @@ pipeline {
             cd /tmp/url-shortener
             rm -rf features spec coverage db/*.db .git* Jenkinsfile *.html 
             cd /tmp
-            tar -czvf ${env.ZIP_FILE} url-shortener/
-            mv /tmp/${env.ZIP_FILE} $CUR_DIR/
+            tar -czvf $ZIP_FILE url-shortener/
+            mv /tmp/$ZIP_FILE $CUR_DIR/
             '''
         }
-        archiveArtifacts artifacts: '${env.ZIP_FILE}.tgz'
+        archiveArtifacts artifacts: '*.tgz'
       }
     }
     stage('Clean up deliverable') {
       steps {
         sh 'rm -rf /tmp/url-shortener'
-        sh 'rm -rf ${env.ZIP_FILE}'
+        sh 'rm -rf *.tgz'
       }
     }
   }