PROCESS=TGZ
UNTGZ=ls

$ eval `echo \$UN$PROCESS`
-bash: TGZ: command not found

$ eval `echo \\$UN$PROCESS`
11getlog.lst  cdt          ...

UNTGZ='tar xzf $ZF'
ZF=../test.org/bar.tar.gz

set -x

$ eval `echo \\$UN$PROCESS`
++ echo '$UNTGZ'
+ eval '$UNTGZ'
++ tar xzf '$ZF'
tar (child): $ZF: Cannot open: No such file or directory

$ eval `eval echo \\$UN$PROCESS`
++ eval echo '$UNTGZ'
+++ echo tar xzf '$ZF'
+ eval tar xzf '$ZF'
++ tar xzf ../test.org/bar.tar.gz