Is it safe to remove the teatimer 1.6.6 update from the Zone Alarm programs list?
Common Sense … Once install, it isn’t needed any more.
If it isn’t needed any more, it will not be run again.
Therefore, it doesn’t have to be in the ZA list.
Will it hurt anything if you leave it there ? NO 
And if it needs access again, such as for an update, it will ask again. Let it out again. Take it off the list still again if you want.
Since this is one of your security programs, why worry about it. If you can not trust your security programs, what is the point of having them?