Technically yes if you code and compile such firmware for them yourself (as there are currently no firmware images available for Elelabs adapters), but practically it is not worth the bother IMHO as too much work for too little gain compared to buying better products that probably cost less than you get if you sell yours. See → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
More is also better so my advice it to have at least three dedicated Zigbee Router devices in a network.
Recommend follow → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Personally, I suggest buying either “IKEA Tradfri Signal Repeater ” or the “Aeotec Range Extender Zi” which are products that work very well out-of-the-box and work better than non-dedicated Zigbee Router devices, while a much more powerful alternative is to make yourself some semi-DIY variant by flashing the correct Zigbee Router firmware to Zigbee Coordinator USB dongles and then using them as stand-alone Zigbee Signal Repeater devices in USB-chargers for power, like, for example, either the Sonoff ZBDongle-E (EFR32MG21 based) or the Sonoff ZBDongle-P (CC2652P) work great as dedicated stand-alone Zigbee Signal Repeaters with recommended firmware. Or if you want to a support community members then check out TubesZB Zigbee Router/Repeater as discussed here.