Number six seed Kerber is yet to drop a set this week and needed just 50 minutes to thrash Cetkovska 6-1 6-0, the Czech qualifier unable to reproduce the form which saw her beat top seed Li Na on Thursday.
"I think I was playing well today," Kerber said. "Petra is a great player and yesterday she beat Li Na so I knew it would be tough."
Kerber will face fifth seed Jelena Jankovic in the semi-finals after the Serbian knocked out former Wimbledon champion Petra Kvitova 6-1 6-3.
Jankovic stormed through the opening set in just 30 minutes and recovered from being an early break down in the second set to win five games in a row.
"I'm pretty confident at the moment," Jankovic said. "I've been very focused this week and played very well so far. Against top players, like Petra, you have to be at the top of your game to have chance to win. I was just sticking to my game plan and luckily it worked. It's nice to be back in the semi-finals here."
The other semi-final will see Romania's Simona Halep take on second seed Agnieszka Radwanska, Halep easily beating fourth seed Sara Errani 6-2 6-0 in just 52 minutes and Radwanska equally untroubled in seeing off Yanina Wickmayer 6-2 6-1.