Four is just two twos but doesn't have three as a factor, so four still isn't equally shareable among three without either not sharing some or, hear me out, murder.
Two pieces equal to 1/3 of the total and two pieces equal to 1/6th. Everyone gets a third with 4 pieces, but one person has two smaller pieces that add up to a third. You can accomplish this by cutting one third off each apple with a single stroke,.
If we can go through multiple apples in a single stroke, then we can assume we're allowed to a) go through the same apple multiple times b) make curved, complex strokes c) murder party members.