The Baggies beat Leicester 2-1 to end Claudio Ranieri's side's 20-match unbeaten run at home in the Premier League which stretches back to September 2015.
West Brom went 1-0 when James Morrison headed in a Matt Phillips cross before Islam Slimani equalised for Leicester with a well taken header of his own.
However, Danny Drinkwater's weak backpass was cut out by Phillips, who went through on goal and scored with a dinked finish past Zieler in the Leicester goal to hand West Brom the three points.
Ranieri apologised to the fans for losing the unbeaten record and lamented the Foxes' first half performance.
"I am very sorry we lost our unbeaten record at home. We knew it would be a tough match against West Brom," the Italian said.
"The first half was not good. We try to have a plan but it was difficult to do this, the second half was much better but we lost the match.
"We made a plan to go on the flank and make crosses from the flank. But we made very few and also we made some long balls and for the central defenders it was too easy. To say something is easy, to do it is more difficult. Maybe we had Champions League fatigue, I don't know.
"The atmosphere was good but of course if you play well the crowd support more. We have to work the crowd. The first half was difficult to enjoy for our fans, the second was much better. I can say only thank you every time to our fans".