You couldn't use Class-Path header in manifest file to point to the JAR's in the JAR file. Please check the following link. You should place the lib folder together with those JAR's in the same folder of myJar.jar.
Adding Classes to the JAR File's Classpath
Note: The Class-Path header points to classes or JAR files on the local network, not JAR files within the JAR file or classes accessible over internet protocols. To load classes in JAR files within a JAR file into the class path, you must write custom code to load those classes. For example, if MyJar.jar contains another JAR file called MyUtils.jar, you cannot use the Class-Path header in MyJar.jar's manifest to load classes in MyUtils.jar into the class path.