Zenden said: "We can't say the tie is over because we're only at half time at the moment. We're in a good position but we still need to be professional and do the job on Tuesday night.
"TNS gave a good account of themselves at Anfield. They were well organised, worked hard and in the end restricted us to just three goals, even though we had chances to score more. We should be more than three goals ahead but hopefully we can score some more at Wrexham and really finish the tie off.
"They have nothing to lose and so they'll look to give us another good game. Obviously we should win because of the position we're in, but I can tell everyone that we aren't complacent. There's still work to be done."