Zulu provider now recognized aside from OpenJDK.

Reasons for distinction are nicely illustrated by Azul's CTO, Gil Tene:

https://groups.google.com/forum/#!topic/mechanical-sympathy/jQGahuzJKM4
https://news.ycombinator.com/item?id=8496003

And on Support forum for Zulu:
https://support.azul.com/hc/en-us/community/posts/200966724-Zulu-vs-OpenJDK-

Since I know of no other OpenJDK binaries which are CERTIFIED to be
TCK-compliant, seems like a good reason to have it.
Another is the fact, that SDKMAN installs it when you chose to install
Java.

libexec/jenv-add

@@ -99,6 +99,9 @@ then
 		if $JENV_JAVAPATH/bin/java -version 2>&1 | grep -q "HotSpot"; then
 			JAVA_PROVIDER="oracle"
 		else
+		   	if $JENV_JAVAPATH/bin/java -version 2>&1 | grep -q "Zulu"; then
+				JAVA_PROVIDER="zulu"
+			else
 		   	if $JENV_JAVAPATH/bin/java -version 2>&1 | grep -q "OpenJDK"; then
 				JAVA_PROVIDER="openjdk"
 			else
@@ -113,6 +116,7 @@ then
           fi;
 				fi;
 			fi;
+			fi;
 		fi;
     if [ $JAVA_PROVIDER=="sap" ]; then
       JAVA_PLATFORM="64"