The No.3-seeded Wozniacki was the first of the pair to advance, rallying from a set and 2-0 down to survive big-serving Karolina Pliskova, 67(3) 63 63. Pliskova blasted 10 aces during the match - including three in a row at one point - but Wozniacki's rock solid ground game was just too much.
"It was particularly difficult to deal with her serve - she was serving very well and playing very aggressively," Wozniacki said. "On these fast courts it wasn't easy, and getting breaks was difficult tonight, but I'm happy to be through. I'm especially pleased with how I played in the third set."
Wozniacki has really been enjoying her time in Monterrey. "The crowd is very nice, the club is very pretty, and it's good that the center court is so big," she said. "And yesterday we went to a typical Mexican restaurant that the tournament recommended to us. I'm just really enjoying my time here."
The No.2-seeded Ivanovic followed with a streaky 61 06 62 win over No.6 seed Magdalena Rybarikova. After storming through the second set, Rybarikova had three game points in the first game of the third to keep the streak going - but Ivanovic fought them all off, broke and never looked back.
"It was a difficult match and she's a difficult opponent," Ivanovic said of Rybarikova. "She mixes her shots up with some slices and it's very tricky, but I'm glad I was able to keep my composure today."
And now, the dream semifinal match-up - Ivanovic leads Wozniacki in their head-to-head series, 3-2, but they are a dead even 2-2 on hardcourts, and being former No.1s, it's going to be a big battle.
"This match will be another difficult one," Ivanovic said. "She returns well and plays very stable."
"Being in the semifinals is a good way for me to start a tournament," Wozniacki said. "There are still a couple more matches to go and I would love to win, but I really need to focus one at a time.
"Playing Ana is never easy. I'm just going to go out and enjoy it as much as I can."
Date-Krumm was the first of the pair to advance, grinding past No.8 seed Monica Puig in a two-hour, 27-minute nail-biter, 64 67(2) 64. The Japanese, a former World No.4, is now through to the semifinals of a WTA event for the first time since reaching the semifinals of Bali at the end of the 2010 season.
Jaksic followed with a 57-minute, 63 60 win over American qualifier Julia Boserup. The Serb is now through to her very first WTA semifinal - she had never even been to a WTA quarterfinal before this.
"I've been giving my best in every match," Jaksic said after her victory. "It's been really tough but I've kept on believing in myself and fighting to the last point, and it's been worth it. This is a great result and I am super excited about it, but there is still a lot of work for me to do here in Monterrey."
The 43-year-old Date-Krumm and 20-year-old Jaksic will be playing for the first time.