Characteristic ZLK timescale (τ_ZLK) for a triple system with an arbitrary tertiary mass (m₃) and outer orbital period (P_out). The system includes an inner circular binary with masses m₁=m₂ = 55 M_⊙ and an orbital period of 1.1 d, at a metallicity of Z = 0.00042, evaluated at the ZAMS. The lines indicate different relevant timescales for the inner binary. The dotted white, dashed black, and solid black lines indicate the circularisation (τ_circ), synchronisation (τ_sync), and apsidal tidal (τ_aps) timescales, respectively. Dark grey indicates dynamically unstable triples.