Two readings, two meanings. As an adverb 'mutually / both sides' it's liǎngxiāng (level tone): 两相情愿 'mutually willing', 两相比较 'comparing both'. As a technical term 'two-phase' (electricity) it's liǎngxiàng (falling tone). Pick the tone by checking the context.
usage
The adverbial 两相 typically pairs with verbs of comparison or agreement: 两相对照 (duìzhào, 'compare side by side'), 两相对比 (duìbǐ, 'contrast'), 两相情愿 (qíngyuàn, 'mutually willing').
