The phrase "mutually causal" can be expressed using a variety of similar terms. One option is "reciprocally causal," indicating a cause-and-effect relationship that goes both ways. Another option is "bi-directionally causal," which also suggests a two-way causal connection. "Interdependent" and "interrelated" both imply a mutual reliance or influence between two or more factors. "Simultaneously causal" conveys the idea of multiple factors causing an effect at the same time. "Concomitantly causal" is another term that suggests a simultaneous causal relationship between multiple variables. Overall, there are many ways to express the concept of mutual causality depending on the context and emphasis required.