The Swiss Railways luggage transfer service will probably take too long, if you dropped of your luggage at a station or had it picked up today it wouldn't arrive at your destination until the day after tomorrow. The service is mainly aimed at people who live in Switzerland.
Due to how the taxi business is regulated in Switzerland / Canton Bern you will likely have to use a local taxi firm for a transfer from Grindelwald
. The road journey from Grindelwald to Zermatt is a bit complicated, the shortest route involves using the car train from Kandersteg
to Goppenstein https://www.bls.ch/en/fahren/autoverlad/tickets/tickets-pkw-kandersteg-goppenstein
and the road from Täsch
to Zermatt requires a permit, which costs CHF 56- p.a. so you might have to change to a local taxi in Täsch or catch the shuttle train from Täsch to Zermatt. If you take a taxi to Zermatt you will dropped off in Spiss at the northern end of the village, from there you will have to take an electric taxi to your accommodation.
It might be worth looking at taking a taxi from Grindelwald to Speiz, a mainline the train from there to Visp and either the BVZ train or a taxi from there to Zermatt.