The Bundesliga giants were tipped to turn over Rangers in the first leg of the tie in Germany, but were left reeling as the Gers turned in a top notch performance and at one stage were 4-1 up.
The defeat has sent shockwaves through the German side, who were forced to deny claims they held a crisis meeting post match.
Zorc admits he is stunned by the defeat and dubbed the result embarrassing for Dortmund, while he fails to understand why the team were not up for playing Rangers in Europe.
He now wants Dortmund to show a reaction in the second leg at Ibrox.
“I’m still shocked. I can’t find the words!” Zorc admitted to German daily Bild.
“It was an embarrassing performance from the first minute to the last, an embarrassing performance.
“Thursday evening, under the lights, not too cold, European competition against a traditional club like Glasgow Rangers, what more could you ask for?
“But the team did not rise to this game, they weren’t ready for this battle. If they have character, they will turn up in the second leg.
“We played sluggishly and did not increase our tempo at the decisive moment. It was an achievement to be ashamed of.”
Dortmund scored a late goal through Raphael Guerreiro to give themselves hope heading into the second leg at Ibrox, but will need a vastly improved performance to have a chance of overturning the deficit and progressing.
