Yes. However, due to a limitation within Marketo, you cannot send the content directly in the webhook.
Fortunately, our platform can connect to Marketo via API and can use the Lead ID to pull in custom object content. Our standard webhook JSON template includes Lead ID for this reason so that if and when you want to include Marketo custom object content, you can easily do so.
If you'd like to explore this capability, please contact us for specific guidance on setup and implementation.