My current split uses front and back squats as such:
Tuesday - Olympic Lifts, Heavy, Front Squats (4 x 3)
Thursday - Conventional push/pull routine
Saturday - Olympic Lifts - Speeed, Back Squats (6, 7 x 3)
IMO Zerchers are more a functional excercise more suitable for strongman training. Front squats are a great quad builder, excellent assistant lift for the olympic lifts, and less strenuous on the lower back.
Also, in general, you should be front squatting a helluva lot more with front squats compared to zerchers.