The Hammers were on course for just a second win of the season until Kieron Richardson's goal deservedly pulled the home side level.
The Italian admitted he could not tolerate the second-half display which denied his side a first win since the opening day of the season.
Zola said: "Certainly their determination, their desire, was superior to ours, simple as that. They just overcame the man light that they had and that was it.
"We lost control of the game. From a game that was totally, totally ours, we let them in and in this league you can't afford that. We had chances after but it was too late.
"From how the team played in the first half we should come out with a victory. To be fair their comeback was remarkable because it wasn't an easy situation."