A gauge covariant formulation of the generating operator Λ, related to the Zakharov-Shabat system L is proposed. The operator Λ̃, corresponding to L ̃ = ψ 0 −1Lψ 0 in the pole gauge is explicitly calculated. Thus the unified approach to the higher nonlinear Schrödinger equations, based on Λ is automatically reformulated with Λ̃ for the higher Heisenberg ferromagnet equations.