Put the Tez tarball libraries in HDFS. Execute on any host that has the Tez client.

su -l <HDFS_USER> -c "hdfs dfs -mkdir -p /hdp/apps/2.3.x.y-z/tez/" 
su -l <HDFS_USER> -c "hdfs dfs -put -f /usr/hdp/current/tez-client/lib/tez.tar.gz /hdp/apps/2.3.x.y-z/tez/."
su -l <HDFS_USER> -c "hdfs dfs -chown -R <HDFS_USER>:<HADOOP_GROUP> /hdp" 
su -l <HDFS_USER> -c "hdfs dfs -chmod -R 555 /hdp/apps/2.3.x.y-z/tez" 
su -l <HDFS_USER> -c "hdfs dfs -chmod -R 444 /hdp/apps/2.3.x.y-z/tez/tez.tar.gz"

where <HDFS_USER> is the HDFS Service user. For example, hdfs.

Save the old Tez configuration and add symlink from /etc/tez/conf:

mv /etc/tez/conf /etc/tez/conf.saved

ln -s /usr/hdp/current/tez-client/conf /etc/tez/conf

ls -la /etc/tez

total 4
drwxr-xr-x 3 root root 4096 Jun 19 21:51 2.3.0.0-2323
lrwxrwxrwx 1 root root   35 Jun 19 21:54 conf -> /usr/hdp/current/tez-client/conf
drwxr-xr-x 2 root root 4096 Jun 14 00:11 conf.saved

From Ambari Web, browse to Services > Tez and select Run Service Check from the Service Actions menu. Confirm the Service Check passes.