Using the fluting toolpath with the parameters set as show in the example above accomplishes exactly what the OP wanted with a single vector. The bit steps down by one pass depth as it returns to the starting point, then steps down again to go forward. No wasteful Z lifts and air passes to get back to the starting point. Comparing it to the same vector cut using a profile pass ON the line the duration of the fluting cut is less than half than that of the profile cut.
4D