Can Orthodoxy speak to eastern religions?
Yes. If the Orthodox speak with the heart and mind of Christ.
In other words, I think the only real, significant difference between Christianity and any other religion is . . . Jesus Christ. Applied towards the East Asian religions (especially, Hinduism and Buddhism), Christianity asserts that Jesus Christ is the only avatar / buddha, precisely because He Is and therefore he is not only an appearance of God in human form (avatar / Gnosticism) nor only an enlightened man (buddha / Ariansim). Instead, He is the only Son of God: truly human, truly a man, one person, Jesus Christ. And He is love.
It is the selfless love of Jesus Christ, in people and shared among people, that Jesus uses to attract people to Himself. That's what worked with me . . . and I had been interested in East Asian religions for years.
Once people find Jesus, then they can be open to receiving the Holy Spirit.
What doesn't work is saying "My spiritual system is better than your spiritual system."
What works, instead, is showing people Jesus. Then, as people respond to Him, they will want to know more about Him and they will want to grow close to Him. Then tell them about the Holy Spirit and how He gives us Jesus, unites us to Jesus, and perfects us in Jesus. And when they ask "how," show them how. Prayer. Fasting. Almsgiving. Loving kindness. The Jesus Prayer. The Liturgy. Etc.
All we have to do is let Him --Jesus-- clearly live through us. He will do the rest.
Two people who showed me selfless love showed me Jesus: without preaching, just by taking care of me when I was very ill.
One priest --a uniate priest, no less-- showed me the Holy Spirit by showing me theosis: in his speech and by his mindset and example.
All that, plus some very good books (especially by Bishop Ware) pointed me towards Orthodoxy.
In short, it all happened and is ongoing by grace: in and through each other.