If you have never noticed, there are two traditions about how to pronounce לזמן at the end of the Bracha of Shecheyanu. Most Ashkenzic Jews in my experience pronounce it as Lazman with a patach under the Lamed (ל). This is also what you will find in most standard Nusach Ashkenaz Siddurim today. The other pronunciation, which is supported by the משנה ברורה and the ערוך השלחן based on the opinion of the רמ”א and מגן אברהם is to pronounce it as Lizman with a chirik under the Lamed. Apparently, this latter form is more grammatically correct. The same is apparently true of Bazman and Bizman.
I am no grammarian. I know almost nothing about grammar. I do harbour a trenchant fidelity towards Mesorah/Tradition, however. This is one of the rare cases where the אחרונים say one thing and the Minhag (Ashkenaz) is not to follow these אחרונים and to follow the סידור אוצרות התפילה
Chabad, amongst others, say Lizman and Bizman.
Picture the scene. It’s an Ashkenazi Shule, always has been. It uses an Ashkenazi Siddur (these days Artsroll but in times gone by Singer). The Rabbi of the Shule is a Chabadnik. He decides to direct the reader of the מגילה on Purim to say Lizman Hazeh and not Lazman Hazeh. When challenged, he says “innocently” that this is the opinion of the מגן אברהם etc.
Will the Lizman vs Lazman kill me? No. Will it make a huge difference in עולם האמת … I doubt it. But it works both ways. If it won’t make that much of a difference, why insist on a מנהג which clearly seems to not be מנהג אשכנז and use the paradox of אחרונים who are Ashkenazim as support? After all, for a Chabadnik, when there is a contradiction between their Siddur and the שולחן ערוך הגרש’’ז they follow the Siddur :-)
It’s the thin edge of the wedge; that’s what bothers me. You just don’t go about lancing an established Mesorah with a chirik.
Disclaimer: I don’t daven Nusach Ashkenaz myself. I have always said Lazman, but I’ve noticed lately that my father seems to say Lizman, so I may well have to change to Lizman myself.